Added extra table in database for the map background layer. Related to Issue [WTI-1087]git-svn-id: https://repos.deltares.nl/repos/WettelijkToetsInstrumentarium/trunk@7998 5a3db67b-de53-47b5-99c8-a1c30a6650e2Former-commit-id: 513a1f3ebd916f12657cea2784df209f6e8b1647Former-commit-id: e4b74c61648d04933880e238fabb20ab3b5109f2