Fixes #2364

Initially, include support only for Gravatar

This adds the concept of independent multi-thread rendering

Credit: Jared

This patch adds to the client interface the ability to filter tickets on the
client portal by help topic, as well as a "clear" feature to clear search,
sort, and filter options.

* Log events for AJAX collaborator list edits
* Avoid extra selects for inline image handling
* Avoid using htmLawed to add target="_blank" and class="no-pjax" to links
  in the ticket thread
* Cache instances of IntlDateFormatter; seems expensive to set up
* Cache filetypes Yaml in APC if available
* Cache I18n::getDefaltLanguage() in the request
* Avoid extraneous usage of Model::_inspect and Model::$meta
* Add aggregated query support to the ORM
* Lazily compile SQL query for InstrumentedLists
* Apply `select_related` setting when setting up InstrumentedList instances
* Slight optimization in SqlCompiler::getField
* Avoid double compiling Sql annotations in the ORDER BY clause
* Cache Thread::getEntries
* Break out event types for ThreadEvent for more legible code
* Eliminate one query from Ticket::loadDynamicData
* Fix ticket number bolding if already answered
* Use dependent subqueries for ticket statistics in the queue page, which is
  significantly faster for large data sets (like hundreds of attachments or
  thread entries)
* Fixup sidebar layout on client knowledge base pages

* Fix crash in Ticket::getLastRespondent
* Fix crash is ORM if using a superclass of a relationship from cache. For
  instance, if the cache contains an ObjectThread instance, but a
  TicketThread instance is required in the relationship. In such a case, use
  the cached data, but change this class. This; however, violates the single
  nature of cache entries.
* Fix spurious events appearing after upgrade due to deleted tickets
* Ensure floating content in thread-body divs does not float past the bottom
* Provide an anchor to thread entries
* Show thread entries before events where both have the same timestamp
* Fix double events for collaborator additions
* Credit email sender with collaborator addition
* Fix incorrect rendering of collaborator addition event
* Fix crash on new ticket due to non-static function
* Fix missing sort on sub-query if explicitly declared in QuerySet
* Fix missing parentheses in SQL for ['field__eq' => QuerySet]
* Fix incorrect SQL on compileSelect for models with inherited $meta['table']
* Dynamically adjust relative time client side

This patch (which needs further development), introduces an extra field to
the %attachment table to store a file's name, in the event that two files
with the same content are stored in the database with differing names. In
such a case, the name is stored in the %attachment table. This allows the
attachment to specify a different name each time the same file is attached
to something in the system.

* Fix attachments not sticking on new dynamic form entry
* Fix attachments not sticking on thread post validation error
* Fix missing inline images in FAQ article viewing
* Fix missing inline images in FAQ article printing
* Fix crash rendering sidebar in staff faq view with attachments
* Rewrite GenericAttachments to be an ORM object
* Port CannedResponse to ORM
* Fix attachments not being displayed when editing a FAQ article
* Fix squirly empty blue box on faq articles with no attachments

The setting is no longer ticket thread specific. Disabling html is now
system wide setting for disable-able textarea widgets as well as email
correspondence.

Also log client edits as an event

This includes adding support to the Redactor editor to force the width of th
editable content to match the width of the displayed content on the client
portal. Also, the landing page displayed on the client portal is themed
(css-class wise) to match that of the Redactor content similar to the FAQ
and thread-entry designer boxes as well.

Also, show sidebar on "Other Resources" pages, and fix a problem displaying
the correct Other Resource page.

Chosen has a problem being rendered in a dialog box with overflow:scroll,
because the content of the dropdown widget is truncated with the scrollable
content of the dialog. Select2 addresses the issue by placing the dropdown
box in the <body> and absolutely positioning it into place.

This patch adds Content-Language and <link rel="alternate"> information to
the client interface for better integration with search engines. It also
adds @lang attribute to the <html> element and various input, textarea, and
richtext boxes for better spell check integration and accuracy.

Fixes #1926

Reset field content when building a new form