Refactor the question implementation.

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>
Merge branch 'master' of https://github.com/opfo/app

* 'master' of https://github.com/opfo/app:
  Add further attrs to posts and questions
  Make OPFModel a protocol
  Add Post superclass and start splitting into models
  Rename Post to Question
  Further prefixing
  Use prefixed class names

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>

Conflicts:
	Code Stream.xcodeproj/project.pbxproj