Case Study can be related to worldwide priority
Test should_allow_association_with_worldwide_priorities

Conflicts:
	test/functional/admin/case_studies_controller_test.rb
Display case studies under a priority

nb: styles on the list are inherited from mainstream which should be
fix soon

Conflicts:
	app/models/worldwide_priority.rb
	app/views/worldwide_priorities/show.html.erb
Add other assoications to wwp
Adding admin form for association to wwp
Fix test for association_with_worldwide_priorities

ActiveRecord::HasManyThroughNestedAssociationsAreReadonly
Condition is covered by :source
Reword step definitions to be more specific

So we can use the same for for worldwide priorities
Allow documents to be associated with priorities
Merge commit 'e9b50853d6b1870a3d5753b503beb80eaf2013d8' into documents-worldwide-priority
clean up merge
Remove duplication

After merge, worldwide priorities were being listed twice
Merge branch 'documents-worldwide-priority'

Tracker: https://www.pivotaltracker.com/story/show/42888611

Also see: https://www.pivotaltracker.com/story/show/45719679 as there
was some overlap.