Implemented exporter and writer for grass cover erosion inwards configurations. Extracted general concepts from WaveConditionsInputConfigurationSchemaIdentifiers and WaveConditionsInputConfigurationWriter. Related to Issue [WTI-1153] git-svn-id: https://repos.deltares.nl/repos/WettelijkToetsInstrumentarium/trunk@8711 5a3db67b-de53-47b5-99c8-a1c30a6650e2