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
Optimize slug generation

This change vastly improves the slug generation speed when there's
a lot of descriptions that have the same name.
Disable index (digitalObjectLoadTask)
Cosmetic changes and migration fixes
Add 2.x migration: activate Dominion
Create context instance
Merge branch '1.x'

Conflicts:
	lib/task/tools/purgeTask.class.php
Compile CSS
s/qtDominionPlugin/arDominionPlugin
Rename final CSS dir
ES fixes
Return false
Add displayTemplate field in the user interface

Update DC, ISAD, MODS and RAD. Refs #3891.