Remove unused application controller filters
Fix undo update presentation bug (stone highlighting)

Also close modal if any new game updates are received. This prevents
no longer relevant undo requests from causing changes.
Simplify sending of game events realtime

Remove code that was used for the old, overly-complicted process,
along with some other unused code.
New processs:
- Generate custom token everytime someone opens a game,
- Send this token to Node.js from browser via websockets (to associate with socket.id)
- When pushing reatlime updates (games#update, games#request_undo),
  include the token so that Node.js knows which sockets to skip,
  as it pushes the updates via websockets.
Add improved security measures for undo actions

Include signed & encrypted move number as hidden field for undo approval form
If an undo is approved, only execute if move number data verifies, and is equal
to current game move number
Also fix small bug for gameshelper.move_status_message
Miscellaneous code cleanup

Also add rescue block for ApplicationController.decrypt_data, to prevent
the entire app from crashing if someone sends bad data