#10 show multiplicity restriction violated exception

[ABresk]

- if somebody tries to remove an object of an entity, which has a multiplicity restricted relation to an other entity in the DAO-layer is performed a check with two possible results:
* removing the object doesn't violate the multiplicity restriction -> removing allowed
* removing the object violate the multiplicity restriction -> removing not allowed -> throwing a DataAccessServiceException with a message, wich is explaining to problem
- at the moment there is only a standardized error message, that it is not possible to delete the data

- showing the detailed error message too, has a benefit for the user, because he or she become a clue why the remove-action doesn't work

-> showing the detailed error-message in the client-error-window