Item12806: ensure foswiki lib is on path for pre-commit

git-svn-id: http://svn.foswiki.org/trunk/core@17416 0b4bb1d4-4e5a-0410-9cc4-b2b747904278
Item12806: document the test mode better

git-svn-id: http://svn.foswiki.org/trunk/core@17417 0b4bb1d4-4e5a-0410-9cc4-b2b747904278