Implemented functions to retreive next ids from database for drones,commandstations,sessions in DCPServerBackendCentral.
Added database connection to CentralStation program.
Changed start id to 1 for sessions. 0x00 is a special value to say hello to central station.
Added open db.
Changed check operation on max value returned when quering db for next ids. 0 is allowed, it will have the first id equaling 1.