updated the method delete(OperationTeam), removeStaff() has now the according return object with no opStaffs, deleteOPStaff() will now querie if the opStaff is in a team

general small changes and first tests for operationTeam. Has error when deleting opStaff. Also deleted TeamMember

Updated Table opStaffsinOperationTeams: removed Primary and set the Foreign Keys opstaffsId and operationteamId as the Primary Key.
Updated the assignStaff method.

Implemented reference for Operation to OperationTeam, only thing to do is the orElse() Function in OperationServiceImpl.java Z.61

operationTeam ist fertig

Implemented Teammember with Reference to OPstaff and OperationTeam and added the method assignStaff()