Fixes tree cache - fixes the unit tests associated with the tree cache so they run properly, tree cache can now be cleared by section, by key, by both or all. There's no longer a default cache key since we don't want to cache things when not needed. ONLY the main trees are now cached, tree pickers and dialog trees should never be cached since tree structures change all of the  time (i.e. by other users, changing node names, etc...). The tree-picker directive also had a cache which meant that anyone using that directive would end up with the same cache.