Refactoring backup system api + Allow plugging auth service for api
Fixing mbs restart-backup-system +  SIGINT/SIGTERM handlers
Use graceful stop for sigint singnals
Switch args in delete-backup/get-backup-database-name to be in query string to be consistent with other methods
Move source info to upper level doc
Wrapping flask with tornado and allowing configuring protocol and ssl options for api server
better naming : rule to path
Merge branch 'api_refactor'