Tokens API additional models

1. Added a test data file and more unit tests for the tokens api access model.
2. Completed fleshing up all models included in the tokens api access model.
3. Finished testing the tokens api access model.
4. Renamed the tests folder to metatests.
5. Completed fleshing up all tokens api response models.
6. Fixed code review issues.
7. Refactored reponses models and added a new test in access_test.py.
8. Rebased changes and uploaded a new patch set.
9. Fixed reviewer comment - made access.json in a more readable format.

Change-Id: Ifb5c03a4de622dc0ed29485fc26e354632c777c3
Adding behavior response for creating and getting secrets/orders

Change-Id: I589feb6568974722a5025a1032f85b2a117548fe
Merge "Adding behavior response for creating and getting secrets/orders"
Fixing redundant states

Change-Id: Iace086ebd2bd2b4d15d43308816504dfc99500b3
Added common Constants file under Cloudcafe project

* Common constants file added to have Messages related constants used in
all projects

Change-Id: I961354a89cb23f00b7557ea0fdbd3bae17f95380
Merge "Tenants API Client - Service Tests Parity"
Merge "Tokens API additional models"
Merge "Added common Constants file under Cloudcafe project"