Added base implementation for writing wave condition input to XML. Related to Issue [WTI-1159]git-svn-id: https://repos.deltares.nl/repos/WettelijkToetsInstrumentarium/trunk@8655 5a3db67b-de53-47b5-99c8-a1c30a6650e2Former-commit-id: 544cb3b3396407a4661089d193a1f12c3c0f7b38Former-commit-id: 97797ef54ed654eae7a6e3f7dd73408ff5061d0e