Credit: Jared

Allow fields without data to do house-cleaning on deletion.

This fixes a strange issue where the first field of a custom form stapled to
a ticket is not populated with data sourced from the API.

Support ability to include attachments to FreeTextField.

This is required with the connection to Dept::getEmail()->send(...)

Ensure that for entries having the same create timestamp, the ID sequence
number is used so that entries inserted first are rendered first in the
thread.

9ae01bf2 turned off HTML balancing, however,
quoted response removal will create unbalanced HTML. That HTML will be
stored unbalanced and will require extra processing when displayed on the
ticket thread.

This patch adds balancing support using libxml if enabled, which will
balance HTML without corrupting the HTML like htmLawed will with balancing
enabled.

The bug was partly due to switch to ORM.

This is necessary for auto-assigned tickets

This patch adds to the client interface the ability to filter tickets on the
client portal by help topic, as well as a "clear" feature to clear search,
sort, and filter options.

* Fix search on boolean field

* Fix crash visiting tasks page while ticket adv search
* Fix search on custom fields
* Add search on ticket source
* Move more advanced fields to drop-down

* Log events for AJAX collaborator list edits
* Avoid extra selects for inline image handling
* Avoid using htmLawed to add target="_blank" and class="no-pjax" to links
  in the ticket thread
* Cache instances of IntlDateFormatter; seems expensive to set up
* Cache filetypes Yaml in APC if available
* Cache I18n::getDefaltLanguage() in the request
* Avoid extraneous usage of Model::_inspect and Model::$meta
* Add aggregated query support to the ORM
* Lazily compile SQL query for InstrumentedLists
* Apply `select_related` setting when setting up InstrumentedList instances
* Slight optimization in SqlCompiler::getField
* Avoid double compiling Sql annotations in the ORDER BY clause
* Cache Thread::getEntries
* Break out event types for ThreadEvent for more legible code
* Eliminate one query from Ticket::loadDynamicData
* Fix ticket number bolding if already answered
* Use dependent subqueries for ticket statistics in the queue page, which is
  significantly faster for large data sets (like hundreds of attachments or
  thread entries)
* Fixup sidebar layout on client knowledge base pages

* Fix crash in Ticket::getLastRespondent
* Fix crash is ORM if using a superclass of a relationship from cache. For
  instance, if the cache contains an ObjectThread instance, but a
  TicketThread instance is required in the relationship. In such a case, use
  the cached data, but change this class. This; however, violates the single
  nature of cache entries.
* Fix spurious events appearing after upgrade due to deleted tickets
* Ensure floating content in thread-body divs does not float past the bottom
* Provide an anchor to thread entries
* Show thread entries before events where both have the same timestamp
* Fix double events for collaborator additions
* Credit email sender with collaborator addition
* Fix incorrect rendering of collaborator addition event
* Fix crash on new ticket due to non-static function
* Fix missing sort on sub-query if explicitly declared in QuerySet
* Fix missing parentheses in SQL for ['field__eq' => QuerySet]
* Fix incorrect SQL on compileSelect for models with inherited $meta['table']
* Dynamically adjust relative time client side

And also fix mishap events changing the ticket status

Add multiple sticky bars support
Make scroll-up automated and independent

This is one of the last milestones for osTicket on an ORM. Unfortunately, it
doesn't make any remarkable speed increases at the moment.

The ORM will cache the structure of the underlying tables (fields and such)
in APC, and will needs to ensure such data is purged when the table
structures change.