Update contributing instructions
Move django_gpg literals to their own module
Import from the correct module
Fix links namespaces
Remove blind capitalization of messages
Split MayanViewM into MayanView and ExtraContextViewMixin, add object permission check to the SimpleObjectLiveView
Add get_extra_context method to ExtraContextMixin
Convert the document_list view to a class based view
Convert the folder documents view and the tag folders view to class based views