Fixed #1278: hide submitdate in browse responses for surveys with datestamp set to no because the conventional timestamp (1980-01-01 00:00:00) is not relevant for end-users

git-svn-id: file:///Users/Shitiz/Downloads/lssvn/source/stable_plus@3525 b72ed6b6-b9f8-46b5-92b4-906544132732