Followon from previous commit: clean up error message helper calls.
Followon from previous commit: remove unneeded message (form already has errors)
Refactor auth/login/reauthenticate a bit.
- left same net results, same events fired, and same messages sent.
- collected all auth-related code in Auth class
(from Hook_GalleryEvent, Login/Reauthenticate/Rest/Users controllers).
- streamlined API using validation rules.
- put error messages in callbacks so they can be used elsewhere
(e.g. reauthenticate to change email/password).
Revise Formo templates - improve how form/group $title and html() are rendered.
Revise Reauthenticate form rendering - now works as typical ajax dialog.
- use Response::ajax_form(), just like almost all other ajax forms in Gallery.
- remove separate view file.
Add events to login and reauthenticate forms (useful for forgot password, register new user, etc.).
Fix continue_url in login and reauthenticate so it isn't persistent.
Fix formatting in gallery.common.js.
Allow dialog links inside dialogs to replace the dialog (e.g. "forgot password" link in login)
Make non-ajax form spacing more consistent with ajax forms.
Add Formo::add_after_submit(), which works just like Formo::add_before_submit().
Revise Login form rendering, move "forgot password" link to user module.
- they now work as typical ajax dialogs, just like reauthenticate.
Merge pull request #365 from shadlaws/fixes_20130513

Fixes 20130513