Remove unused collections stuff

This was a beta api that didn't work out.

Test plan:
  canvas should still work (sorry, this touches lots of stuff)

Change-Id: I31680b83f72f6d739ce74735ba40d7a760debb33
Reviewed-on: https://gerrit.instructure.com/29506
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jon Jensen <jon@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Cameron Matheson <cameron@instructure.com>

Author: cmatheson

app/controllers/application_controller.rb

@@ -409,10 +409,6 @@ def get_context
         params[:context_id] = params[:course_section_id]
         params[:context_type] = "CourseSection"
         @context = api_find(CourseSection, params[:course_section_id])
-      elsif params[:collection_item_id]
-        params[:context_id] = params[:collection_item_id]
-        params[:context_type] = 'CollectionItem'
-        @context = CollectionItem.find(params[:collection_item_id])
       elsif request.path.match(/\A\/profile/) || request.path == '/' || request.path.match(/\A\/dashboard\/files/) || request.path.match(/\A\/calendar/) || request.path.match(/\A\/assignments/) || request.path.match(/\A\/files/)
         @context = @current_user
         @context_membership = @context