Fix request body and response documentation being the same

Add some tests for generation of request bodies and improve the
tests for responses.

Tidy up some unused imports.

!BUG:MUSAPI-89
!TEST:
Look at generated REST documentation and see that the examples for
request bodies and responses are no longer identical. A simple
example is AlbumController PUT /albums/{albumId} where the request
should only contain id fields for artist, genre, contentManager
and image unlike the response.
Replace tabs with spaces