Adds the mgmt APIs for
1. Create datastore-version.
2. List datastore-versions.
3. Get details of a datastore-version.
4. Update the attributes of an existing datastore-version.
5. Delete a datastore-version.
Added the code to management.py and the unit-tests,
this code would help for writing integration tests to trove
for the newly added management-apis.
Change-Id: I915baa4c5c8bbe3f0483bcaeaa5ce95044d35bf7
Implements: blueprint datastore-registration-api