Upgraded jQuery UI to Release 1.11.12.   Still need to convert to new style datepicker internationalisation, but the old style works for now.

git-svn-id: http://svn.code.sf.net/p/mrbs/code/mrbs/trunk@2892 25f7e783-145e-4f2d-a9f8-dd7182bfe9c7
Removed the session_save_path writability test as it's not reliable.   For example on Windows the session_save_path can fail the writability test but sessions still work.

git-svn-id: http://svn.code.sf.net/p/mrbs/code/mrbs/trunk@2893 25f7e783-145e-4f2d-a9f8-dd7182bfe9c7