[FIX] trackers: Add a way to make jquery validate work on mandatory "old style" html date drop-down groups

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/11.x@46594 b456876b-0849-0410-b77d-98878d47e9d5
[FIX] trackers: Make the required_in_group error only appear on the last field to stop page layout breaking, also improve the error message and make it translatable.

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/11.x@46595 b456876b-0849-0410-b77d-98878d47e9d5