This would be required for new ticket auto-responses to tickets created
without an initial message.

Since tickets can be created without a message now, the emailing system
should also identify the thread the message is associated with, so that a
returning email can be associated with the ticket or task's thread in the
event that it was created without an initial message.

References:
https://bugs.php.net/bug.php?id=43200
http://stackoverflow.com/a/22521203

Also try harder to send a relevant In-Reply-To and References header back
to the client with the email message.

This patch suggests a change to the message-id creation process that
includes stamping the receiving user-id (staff or client) along with the
thread-id of the originating notice. This allows detection of threading if
the clinically brain-dead mail client drops all the other header detection
mechanisms, including the tag placed in the email body, on response.

This patch works for both client and agent communication.

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

Fixes #1660

Refactor filter.yaml and related code base
Move isBanned routine to banlist class and make it banlist specific
Refactor how canned responses get list of filters

This is necessary because group table gets renamed as part of the upgrade.

Don't crash when login-banner page doesn't exist yet.

Make the upgrader play nice when loading latest yaml files.

  * Add trashcan icon for newly-added actions
  * Categorize filter actions
  * Use imperative phrases for action descriptions
  * Drop check boxes from simple actions (like reject ticket)
  * Hide empty forms on new ticket pages
  * Do not store config for nondata fields for actions
  * Implement a multi-use feature for actions, which will allow using a
    action more than once (for instance, multiple email sends)
  * Filter actions are sortable
  * Send email has from address configurable
  * %{user} token is valid as a recipient

This patch rebases filters into a row-based layout and redesigns the filter
apply method to be more extensible. It also redesigns the UI to be more
dynamic and to allow for actions to be added without database modification
and actions can also have complex configurations.

And properly escape and display form title and instructions

Help topics can now specify one or more additional forms to be included on
the help topic and can also specify the sort order of those forms.
Furthermore, individual fields can be disabled per help topic, so that
unnecessary fields can be omitted when necessary, per help topic.

The disabled flag is recorded along side the field data so that the field
will not be accidentally added to the form later automatically. There is no
interface in this commit to enable a field which was disabled by the help
topic when ticket was created.

Don't add to endTime if not already set

  * 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