Add variable replacer callback

is_callable will report ANY function as available

This is necessary because the system depends ticket priority to sort and
display ticket data.

Provide facility to set collaborator status on add.

This patch addresses an issue where a client may have upper-case letters in
their email address. When visiting the client portal to check the ticket
status, previously, the exact same case would be required in the 'Email
Address' box.

This patch remove the case sensitivity for email logins.

Extra forms associated with the help topic are now shown above the ticket
details form on both the staff and client interfaces.

Also add in the user email address after the user name.

This patch also adds an ::export() method to the FormField() class which
allows a field to define how the data should be formatted when exported.

Fixes #390

For use in the materialized view column names

Fix dropping of materialized view when variable name is changed

Ensure view exists before merging updates

Prevent possible sql injection error in field name used in the materialized
view.

Prevent possible xss error in the display of the field label and variable
name in the admin panel.

This is especially important if the html ticket thread is disabled. In such
a case the message body will still be HTML, but an HTML email should not be
sent out.

Fixes #374

(And newer versions don't seem to like the legacy code). This patch uses a
`Refresh` header for IIS versions prior to 7.0 (included with Windows Vista
/ Server 2008). Starting with IIS 7.0, the Location header should be
properly handled by IIS.

Fix adding fields to an existing form

Use a union query to avoid using DISTINCT and lots and lots of joins in the
from clause.

Initial tests seem to indicate about a 80% faster (~500ms down from ~800ms)
on querying about 9k tickets).

And make plugin internal handling more consistent

And install initial data in target language. Also configure help tip
popovers to be in the configured, default system language.

And allow passing a callable array as the callback to the URL dispatcher

This patch introduces an automatic materialized view to speed database
performance when querying and displaying the ticket views. This can
eventually be extended to the search and advanced search features to speed
them as well.

The data from the dynamic form entries related to ticket details is copied
to a %ticket__cdata table. The %ticket__cdata table is then joined directly
to the other tables in the query for the ticket view. MySQL is magically
and dramatically faster using this method.

The downside is that the disk usage for the custom data is doubled, and the
time needed to update the dynamic data is at least doubled as the form
entries and the materialized view must both be updated.

This method should also extend well to other database platforms in the
future. It will be likely that most other database query optimizers will
have difficulty joining, scanning, and sorting the table models we have for
custom data fields.

We introduced a glitch in 29b37144, which was the patch that introduced
matching on email headers other than the Subject.

I misinterpreted the original `preg_match()` regex, thinking that it was
requiring brackets. Looking at it again today, I see that it didn't. The
current one does, however, require surrounding brackets.

This patch also allows for extra letters or dashes between the `#` and the
ticket number. Eventually we should allow the ticket number itself to have
extra characters -- be formattable.

Fixes osTicket/osTicket-1.8#342