Extended functionaliry of WmtsBackgroundDataConfiguration: - Introduced default parameterless constructor which initializes an unconfigured WMTS background data configuration -- Replaced all unconfigured WmtsBackgroundDataConfigurations instances with parameterless constructor - Adjusted BackgroundDataProperties: -- It is not possible to reach a state where a WmtsBackgroundDataConfiguration is configured with NULL values on the properties -- Adjusted affected test Related to Issue [WTI-1141] git-svn-id: https://repos.deltares.nl/repos/WettelijkToetsInstrumentarium/trunk@8952 5a3db67b-de53-47b5-99c8-a1c30a6650e2