Improve test for unsettable fields

Check for static and final modifiers. This catches constants other than serialVersionUID.

!BUG:25422
Create and take note of @DocumentSetterMethods annotation

New style command classes can be annotated with @DocumentSetterMethods and
this makes the document generatator use the setter methods (rather than the
getter methods) to decide what the fields of the command are.

!BUG:25422
!TESTS: Check that the request body is document for PUT /albums/{id} and
the like (once they have had the annotation added).
Merge pull request #8 from brucegodden/fogbugz25422

Create and take note of @DocumentSetterMethods annotation