fix images v1.0 model deserialization

 - refactor deserialization to match raw json model

Change-Id: I1368174ba5d6ec5d0112c3e8a21b1decf549aa44
Tenants API Role Model

1. Added a role model and unit test.
2. Moved unit tests to a metatests package.
3. Rebased changes as per reviewer comments.

Change-Id: Id660ff4b5be7020e90786eed5d5405d78ca9737e