Needed refactoring of submit manuscript flow.
Checks are run via the forms. Also, the copying
of data from old submissions is done via forms.

All this functionality is removed from the model.

Write tests and refactor html.

RequestCommentary is transformed to a class based view. Further
 moved strings to `/strings` and used django.messages middleware
 to pass messages to the user instead of context data.

The acknowledgement message is no longer hardcoded in
theses/views.py, but resides in the top-level strings module.