Use QubitDescription in deaccession form.

Cherry-picked from Radda's fork. Fixes #4286.
Add sf task to manage plugins
Rename file according to its contained class
Support 1.x/2.x db upgrades, refs #4494

Apply new database upgrades selectively depending on the milestone.
Small fixes
Simplify code comment
Add fks support in addColumn (QubitMigrate)
Add information_object.source_metadata_id column

I'm adding an extra column to store the source standard
(refs #3891). TODO: add taxonomy and terms. Migration added,
taking this chance to do more migration testing (refs #4494).
Create lib/task/tools dir
Add dates column to actor/browse, fixes #4444

Squashed commit of the following:

commit 7cf3a5739bc839f158d40722e0746cbd6c0207c4
Author: José Raddaoui Marín <raddaouimarin@gmail.com>
Date:   Sat Dec 22 16:11:29 2012 +0100

    Add dates of existence on actors browse list
Add information object templates taxonomy/terms

Using the new migration scripts (arMigration0094 class, refs #4494),
this commit adds the needed taxonomy and terms regarding to the new
switch template feature based on source standard (refs #3894).
Merge branch 'issue-4494' into 1.x.

Fixes #4494. See the issue page for more details.

New migration scripts are located under:
- lib/task/migrate/migrations/*.class.php
The existing ones can be used as examples.
Ignore non existing columns during migrations
Pass sfApplicationConfiguration to up()
Added task for adding superusers.
Refactored purge task to use log from add superuser task.
Revert schema change in 1.x, it's 2.x only.

Refs #3891.
Fix method declaration, error in PHP 5.4

It was fixed in http://www.phing.info/trac/ticket/555, but the
sfPropelPlugin bundled in sf 1.4 is dated.
Clear the search index from the purge task
Add .class to extension