Sunspot integration: drivers and database

Main points in the pull request:

 - Fixed the definition of Measures table in the database.

 - Fixed "createMeasure" service:

 - "Add" and "remove" methods in sunspot drivers implemented.
             - add() -> register a sunspot in the system, so it is possible to receive measures from it.
             - remove() -> unregister a sunspot. The system won´t receive more measures from this device