Add datehandler unit test

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@22884 4ae1f11a-8b86-4847-b8af-ab372f36d1fd
6871: workaround gtk RTL bug in MultiTreeView

Blend of Nick's and my fix for the bug.

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@22887 4ae1f11a-8b86-4847-b8af-ab372f36d1fd