Add a tab for tasks
Add mass action for tasks

This is necessary to allow objects to register data views on the fly.

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 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.

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.

Introduce the concept of tasks. Tasks are to do list that can be attached to
any object e.g Ticket.

Use generic attachment table for all attachments system-wide.
Drop thread entry attachment table

Detach conversation thread from ticket to make it more generic. Any object
can now have its own thread complete with entry type and attachments.

Use generic attachment table for all attachments system-wide.
Drop thread entry attachment table

Detach conversation thread from ticket to make it more generic. Any object
can now have its own thread complete with entry type and attachments.

Introduce the concept of role-based access for agents.

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.

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

Ticket numbers are now configurable as a system-default and by help topic.
Previously, an administrator could select between six-digit random and
sequential numbers. Now, the sequence is selectable so multiple sequences
as needed, and a format can be specified to define how the ticket numbers
look. Formats can also be defined for each help topic.

Multilanguage Support via gettext

- added gettext encapsulations to all texts i thought necessary
- added fallback function for the case that the gettext extension isn't loaded
- added browser language detection
- added gettext to the list of optional extensions in setup
- rewritten some of the texts to use sprintf instead of appending strings
- added german translation file
- removed mark_overdue-confirm from cannedresponses.inc.php

extend multi language support and a fex fixes

- Better detection of translation files
- Added functionality to redirect language codes (see redirecting
language codes)
- Ticket Status can be translated
- The Datepicker can be translated
- Extended functionality of 'testlang.php' to show what language code is
used to translate

Forgotten to apply a patch from RC5 to RC6

- Forgotten to change $var to $vars in line 380 of class.mailfetch.php
- Removed unneeded comment

Added php_gettext as primary translation engine

- Added php_gettext support (thanks to Danilo Segan and Steven
Armstrong)
- php_gettext is now the primary translation engine
- Extended language detection functionality

Add error/misconfiguration checks and fix undefined variables

First implementation of built-in custom list

The original compatibility functions for the mb_strlen, mb_strpos, and
mb_substr functions was not implemented correctly. This patch uses the PCRE
library to do Unicode processing

No need to execute signal connect for each request!

Connect to logout signal and clear upgrader session on staff logout.