port to 4.6, complete reworking of UI to include tabs, better confirmation...

port to 4.6, complete reworking of UI to include tabs, better confirmation screens for creating and editing, better hook_help implementation, update hook_link to work with new 4.6 event module,  remove db tables rsvp_event and rsvp_user_prefs,  rename db table rsvp_to_user to rsvp_invite, removed user preferences in favor of good defaults, user permissions audit, better email address input validation, invitation url by hash value access is always allowed, all html broken out into rsvp.theme file and theme functions, pruned rsvp.css