Made properties Intredepunt and Uittredepunt read-only, based on the surface line that is present on the piping intput. Prevented the possibility to import a calculation for which entry and/or exit points are defined without a surface line. Related to Issue [WTI-1051] git-svn-id: https://repos.deltares.nl/repos/WettelijkToetsInstrumentarium/trunk@8563 5a3db67b-de53-47b5-99c8-a1c30a6650e2