Fixes a bug where a lock icon is shown on tickets listing even when the lock
in question is expired.

Load and cache all the attachments on a thread prior to rendering the items.
That removes the need to run a query per thread item to check for- and fetch
attachments.

This feature allows (by option) an organization to allow its members to see
tickets from other members. It can be used beside or instead of the
automated collaboration feature. Now, collaborators retain access to tickets
on which they participate; however, sharing can be used to enable access to
other tickets owned by their organization.

Redirect to recent queue / listing on transfer or assign

Utilize the same template for tickets and tasks queues

Disable pjax on task print

- Adds mass assign, transfer to ticket queues
- Retire inline forms for ticket assignment and transfer

And two flags, one which signals that stored HTML is correctly balanced and
does not need to be balanced when rendered in the ticket view. The second is
used to signal messages received from collaborators.

Additionally, this patch fixes showing external inline images (via the [Show
Images] button) when clicked.

Implement generic get dynamic fields lookup routines

- Tickets cannot be closed when an open ticket exists
- Tickets/Tasks cannot be closed when required for close fields are missing
data
- Add isCloseable routine to ticket/task classes

Initially, include support only for Gravatar

This patch shores up the new list management feature with the custom list
handler feature written to support lists being saved in a table other than
%list_item, namely the built-in ticket status list.

Also squelch the 'You sure?' popup appearing multiple times.

Restrict view access depending on agent's perm.

* Make the "Items" tab the default
* Drop the "Showing ..." text and add a count to the items tab
* Redirect to "Items" tab when creating a new list
* Add a new list item by ajax rather than refresh