Add tests for REST error responses.
Rename a couple Rest_Items_Test tests (no functional changes).
Move Rest_UserComments from gallery to comment module.

--HG--
rename : modules/gallery/classes/Gallery/Rest/UserComments.php => modules/comment/classes/Comment/Rest/UserComments.php
rename : modules/gallery/classes/Rest/UserComments.php => modules/comment/classes/Rest/UserComments.php
Fix class declarations for newly-renamed classes.
Refactor Rest_Tree::get_members() a bit.
Add REST unit tests for tree, user_items, users, and search.
Merge pull request #427 from shadlaws/fixes_20130623

Fixes 20130623