Make sure that mappings controls are only shown when the user has the
required authorization to perform the mapping. Further, only show items
that can be mapped in the modal dialog for mapping. This required quite
a bit of refactoring.
Fix modal selector for mappings without specified context
Move Permission object to its own file
Merge remote-tracking branch 'origin/develop' into feature/restrict_map_to_page

Conflicts:
	src/ggrc/assets/javascripts/mustache_helper.js
Fix mappings to and from objectives
Don't show stubs in lists, only full objects
Don't use getRootModelName anymore
Avoid duplicating work in Resource#get
Fix issues with modal selector
Enable indexing of Person, Document, and Help models
Merge remote-tracking branch 'origin/develop' into feature/restrict_map_to_page
Improve tolerance for objects with null context
Merge pull request #298 from reciprocity/feature/restrict_map_to_page

David's changes to fix permission checks and a variety of minor fixes