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 patch converts the central file and threading classes over to use the
ORM.

  * Fix missing attachments join for Category (fixes #1654)
  * Fix crash on user account registration
  * Fix save button on user account (fixes #1655) — regression from bebc2d79

  * Fix incorrect mapping to user email address
  * Fix early rejecting of tickets — even if a filter earlier in the
    matching filter list had "stop on match" set
  * Fix ::stopOnMatch referring to incorrect db field

The new logic abandons the early rejection logic in ticket create. Instead,
the normal validation is completed as usual. Thereafter, the filter is
initialized and applied to the ticket. Upon rejection, a RejectedException
is thrown by the ::apply() method of the TicketFilter. The Ticket::create()
method will handle the exception and reject the ticket.

Add generic routing to get object's dynamic form entries.

This allows for things like related COUNTs and such:

```php
ThreadEntry::objects()->annotate(
    'attachment_count'=>Aggregate::COUNT('attachments')
    )
    ->filter(array('attachments__type__contains'=>'image/'))
    ->filter(array('attachment_count__gt'=>0));
```
This would find all thread entries with at least one image attached.

This patch fixes a small glitch where validation might be bypassed for
fields for agents. Previously there was a glitch where required fields would
have their validation errors ignored.

Since users can already log in via their email address, offer a friendly
error message when agents configure the user name to be an email address.

This will be useful for maintaining arbitrary list of items. ListObject
should be used in the place of ArrayObject

Fix issue that fails for get names on incorrect formats. Ex: J.Everybody

And allow for @context to add context to the bare string literal. For
instance,

    /* @trans, @context "noun" */ 'Open'

Would mark the string 'Open' translatable with context "noun".

Statuses with tickets cannot be deleted
Fix orm to class gracefully when joins are not inspected
Add create date to new statuses

Names parsed from incoming emails are stored in the database as is. This
pull request addresses potential XSS vulnerability due to improper display
of unsanitized names. Going forward names will be scrubbed on create.

Fixes #958

Add ability to disable canned responses
Fix team drop down selection
Remove priority escalation setting in SLA page (implementation is on todo
        list)