Add SQL patch file and update the main install SQL (MySQL) script to
transfer messages, responses, and notes into the new ticket_thread table.
For new installations, transfer is not necessary because there are no
messages

Replace the ticket_{message,response,note} tables with a single
ticket_thread table that will contain data for all three current message
types. This simplifies much of the ticket thread code and paves the way for
other types of messages in the future.

Track assigned department, team, staff, and help topic when the ticket event
occurs. This will greatly help in correlation of various reports and queries

Also start plowing the way toward incremental database updates using a
patching technique. The hash of the main install SQL script for a respective
database will be used to track the signature of the database currently. The
signature will be stored in %config::schema_signature, and the main.inc.php
script can simply check the value in the schema against the value known to
the source code to be the signature the code expects. Should the two
signatures differ, patches in the setup/inc/sql/patches folder should exist
and be executed to assist in incrementally upgrading the database to the
new-current schema version.

Assignees refactored.

Pull request #35-40. Co-reviewed by Jared & Peter on 04.01.12

Feature/ticket open typeahead

Track history of tickets over time for snazzy dashboard reports

Feature/discard warning + ticket preview enhancements

Add CSV (Excel) export option to ticket search results

Adds a link to the scp/tickets.php page (Tickets) allowing for the export of
the data to CSV file. This is preliminary and still needs a few items:
  * An icon + button CSS definition
  * Support for alternate columns (staff assigned, etc.)

Also add beginnings of complex export support (PDF, JSON  and other
formats
to follow). CSV is fully supported for now.

And for brevity, add a Http::download method to allow for consistent and
browser-independent forced page content downloads