Also, add warning popup when lock is about to expire and allow the user to
attempt to renew the lock. Also, connect the keyup callback for redactor to
the autoLock.handleEvent for greater update of the lock, and also deadband
the lock to every 10 seconds.

This patch includes a slight database migration, and adjusts the
functionality of a few core components.

  * Move collaborators from the ticket to the thread.
    This concept allows collaborators on any object which has a thread,
    including tasks.

  * Add flags to the thread entry
    This will allow flagging thread entries for different purposes.
    Initially this can be used to flag the original message of a thread in
    case a ticket / thread is created without an initial message.

  * Lock becomes more of a utility
    The lock is now disconnected from the ticket and is a separate utility.
    Separately, the ticket and task objects can have a reference to a lock
    object. Furthermore, when submitting some activities to tickets, the
    lock is verified to be owned by the respective agent, and the lock code
    must match a current lock code. The code is rotated on each acquire()
    call to guard against double submissions.

  * Collaborator is an ORM model
    The TicketUser class is broken up now so that the collaborator instance
    can exist apart from a ticket. Email message ids are now generated for
    collaborators without respect for a ticket so that collaborators can be
    properly supported on any thread.

This script adds a single download script, 'file.php', which provides access
to files of all types to all users. It uses a HMAC signature system with an
expires time, which allows signed URLs to be sent to external users.

This also fixes an issue with the Http::cacheable() method, where the
last-modified and Etag headers were not properly compared, which resulted in
permanent cache misses by the client.

Also, autodetect the endusers timezone using the jstimezonedetect Javascript
library.

This patch adds support for automatic date and time formatting based on a
selection of locale. The locale can default to the system or user specified
language+locale, or can be elected separately. For instance, English
speakers can pick between US, GB, and many other English speaking locales.

This also removes the need of the %timezone table and uses the timezonedb
built into PHP 5.3+. User's can now select from a much longer list of
database and no longer need to deal with the DST checkbox.

The solution is simple: upload the image, create the draft automatically,
attach the image to the draft, return the draft_id to the client. That's it.
There's no more need to create the draft in advance now.

Instead, only show the box if the draft has been modified since initially
created / updated.

  * Use the title of "Information" with internal tag of "info"
  * Add "Visibility" column to UI and retire "Required" and "Internal"
    columns
  * Add visibility selection to new fields and show visibility to the user
    information fields when displayed on the ticket details form
  * Make the visibility settings translatable
  * Use constants internally for visibility configuration detection
  * Use a larger input when managing the information HTML content
  * Fix validation errors for new fields
    * Enforce new field name uniqueness
    * Enforce new field name character validation

The staff portal has a feature where the date fields are converted to
YYYY-MM-DD prior to form submission. However, this code was not ported to
the client portal. Therefore, for non-US date formats (d/m/Y for instance)
would not be processed properly by the server and would be nulled prior to
validation.

Only one file is supported at a time now; but at least the files are saved
and displayed in the event of validation errors.