Fix Control inheritance order to not break eager_query
When building a polymorphic link, don't touch the target

* this saves a query per object
* also, change 'Context#related' to 'related_object' to match the
  standard
Merge remote-tracking branch 'origin/develop' into feature/various-fixes
Change eager-loading strategy on a few join models
Don't require 'X-Requested-By' header on GET requests
Make two common methods slightly more tolerant
Fix JSON builder to return the correct 'type' value

* in some cases, it was returning the type attribute as the value of
  'type'
Fix Category inheritance order and eager loading
Enable options and categories in modal forms

* add option_select and category_select mustache helpers
Attempt to fix Categorizable.eager_query
Add test to verify query count for each service
Add missing relationships to various pages
Handle inheritance in association_proxy targets
Move some more templates into assets/mustache
Move all templates known to be used to assets/mustache
Fix issue in multi-type selector
Merge remote-tracking branch 'origin/develop' into feature/various-fixes
Fixes to get unittests passing again.
Merge remote-tracking branch 'origin/develop' into feature/various-fixes

Conflicts:
	src/ggrc/assets/mustache/documents/list.mustache
	src/ggrc/models/category.py
	src/ggrc/models/context.py
Add back 'one()' usage and fix response to return 404