Implement Database as a Service (Trove)

MySQL database :white_check_mark: 
Keystone resources :white_check_mark: 
Load-Balancer :white_check_mark: 
Common class :white_check_mark: 
Controller classes (API, conductor, taskmanager)  :white_check_mark: 
for now, yes. It's for testing purpose. For the release, we will indicate a specific commit ID