feature: ACL (Access Control List)

This adds a new feature called ACL that offers the ability to control what
IP addresses are allowed to access the system. This adds a new textfield to
the System Settings to add a comma separated list of IPs. This also adds a
dropdown labeled "Apply To:" that gives you the option to choose which
panel(s) the ACL will apply to. Lastly, this adds a validator for a simple
comma-separated list of IP addresses. (eg. `192.168.1.1, 192.168.2.2,
192.168.3.3`)

If the requester's IP is not in the ACL the system will show an "Access
Denied" page. If the requester's IP is in the ACL they will be able to
access the system as usual. If the ACL field is set to Disabled, anyone will
be able to access the system.

This adds an initial failsafe where if the Admin's current IP address is not
in the ACL upon saving the system will refuse to save the setting to prevent
the Admin from being locked out. This also adds another failsafe where if
there is an "Apply To:" option set but there are no IPs provided the system
will return an error letting the Admin know they have to insert an IP
address to continue.

issue: Choice Validation Accept Punctuation

This addresses issue mentioned in 4071 where the choice field validation is
not accepting punctuations. This updates the regex to accept anything the
user inputs. This introduces another issue that if the choice contains `:`
in the value then it will truncate everything after. This is due to the
explode method that explodes on any `:` character. This updates the explode
method to return only 2 values which only explodes on one `:` character
which returns the full value.

issue: Organization Ticket Export No Filename

MPDF Issues

1. Task Exports: This commit fixes the contructor for printing Tasks using MPDF

2. PDF Formatting: This commit fixes an issue where the header of each thread entry did not stretch across the page correctly. This was an unintentional side effect of trying to fix the way HTML tables printed in PDFs.

3. FAQ PDFs: This commit passes the correct values to mPDFWithLocalImages when printing FAQs

This addresses an issue where clicking Export on an Organization's Tickets
will export a file with the filename of 'csv' and no extension. This is due
to the variables we are passing to the `saveTickets` function. We are
missing a variable called '$fields' that contains a list of fields.

issue: iFrame On Install

Issue: Ticket Export Headers

This commit fixes an issue where custom export headings were being set to numeric values rather than field labels.

For exports that are already saved, we can get the heading directly using getHeading. To get the heading for fields that are not already saved as exports, we can use getExportableFields, which will return path => heading.

Issue: Choosing Fields to Export

This addresses the "Call to getAllowIframes() on NULL" error on installation
pages. This is due to 4781 that introduced the concept of allowing multiple
iFrames, where we are not checking for `$cfg` before calling the method.
This adds a check for `$cfg` so the errors do not occur.

oops: Thread Variable Fatal Error

oops: Emojis Strip Korean

This addresses an issue where Korean text is stripped from the body. This is
due to the strip_emoticons function, as Korean text is in the same unicode
range as some of the emojis.

This addresses an issue introduced with 4737 where using `%{ticket.thread}`
causes a fatal error. This is because `ObjectThread->asVar()` returns an
object which cannot be converted to a string. This adds a `__tostring()`
function to class ThreadEntries so it can be converted to a string properly.

iframe: Allow Multiple iFrame Domains

This commit fixes an issue where only the saved export fields would export, whether you checked more fields to export or unchecked some of the saved fields.

For any fields not saved that need to be exported, we need to find their label and then put it in the fields array. For any saved export fields that are unchecked, we need to compare what was checked vs what is saved and then unset the fields that were unchecked.

issue: Maxfilesize Comma Crash

variable: Complete Thread ASC or DESC

Issue: Saving Checkbox Values

Issue: Duplicate Tickets in Closed Queue

This pull adds the ability to choose between ASC or DESC order for the
complete thread variable. If `complete_asc` is chosen the system will order
the thread in ASC order, if `complete_desc` is chosen the system will order
the thread in DESC order. This keeps backwards compatibility with just
`complete` as some people might forget to update this for a while.

This commit fixes an issue where checkboxes could not be edited for inline edit or all field edits.

When a BooleanField is directly passed to the to_database method, you are not able to accurately check to see if old != new. To fix this, I added a new getChanges method to the BooleanField class that will first do a comparison on the raw boolean value (true, false) and then get the value needed for the database. I then made sure that we use that new function when editing all fields together.

Additionally, I added a getClean method to the BooleanField class so that $this->_clean for the field would be set to either true or NULL depending on if the box is checked or not and would accurately save to the database when calling $form->saveAnswers()

Assignment Restriction Issue

This commit fixes an issue where we were not checking the restrictions on Ticket assignment correctly. isAccessLimited returns true if showAssignedOnly is true, so we wouldn't want to negate the isAccessLimited check (that would return true if access is not limited).

Also, if an Agent's access is limited to assigned tickets only, we can return the assigned tickets once we have them without needing to go through any further processing.

Finally, we should still allow an agent to view an assigned ticket even if the ticket is closed.

Note: queue counts update themselves a little after you toggle the 'Limit ticket access to ONLY assigned tickets' check box. The 'See all tickets in search results, regardless of access' still works correctly as well.

issue: Strip Emoticons

Quick Filter Fixes:

Make the following work:
- Assigned
- Assignee
- Department Manager
- Assigned Team

Also, make sure we account for if there are no choices available for a quick filter Ex: The helpdesk does not have any teams

issue: APC CLI

Issue: MPDF Export PHP < 7.0

Fix bug: send new ticket alert to account manager

    This commit fixes an issue where using MPDF to print Tickets did not work if the PHP version was < 7.0 because MPDF called the random_int function which is only available for PHP 7.0+. Now, we check the PHP version before printing, and if it is less than 7.0, we use the rand function. If it is >= 7.0, we continue to use the random_int function.

issue: Multilingual FAQ Category w/ Parent