Add mgmt API for datastores

Implemented mgmt API calls for create/update datastores/versions.
To access this API call "admin" role is required.
Removed datastores related commands from trove-manage.
Changed response from datastore-list, now regular user can see only
datastores which has atleast one active version.

Change-Id: I49195c2c8c08fe4673b2dc69d86ea16ee7654431
Implements: blueprint datastores-mgmt-api
Depends-On: I01c0ecc276a73fbbc06ec39bfaa1c66f47fc3a9c Trove
Depends-On: Iee7ed7b141548ef64231acad6319e769d356b97f python-troveclient