Split code; Start work on android version
[Android] Start work on debt view
Revert "[Android] Start work on debt view"

This reverts commit f030cd4b9d2514cc5ab5af7ef5386a3e8308ef72.
[Android] Start work on debt view
[Android] Fix error message when logging in with incorrect information; Add buttons and comment on debt views
[Android] Start work on accept/decline/complete debts
[Android] Modify AndroidConnection to run sockets in own threads (as required by Android)
Commit message:
Done:
- Introduce (incomplete) secure connection classes
- Start work on session tokens (for android)

TODO:
- Finnish secure connection classes
- Finnish session tokens system:
	* Make sure user gets all necessary updates when receiving new
	  handler (ServerConnectionHandler:114)
	* Pass connection and received object to correct handler when
	  detected (ServerConnectionHandler:106)
	* Create system for assigning session tokens to new connections,
	  and send them to the client
Commit message:
[Server] Make sure all (possible) updates are sent to a user that has lost
its handler, when getting a new handler.
[Core] Make Session.processUpdate() handle not changed updates also.
Continue work on session token system. Still a little bugged!
[Android] Fix accepting (and possibly declining and completing) of debt. GUI still doesn/t update though.
- [Android] Fix updating of GUI when accepting/declining/completing debt
- [Server] Fix bug that caused the server not always to attach session
  token when responding to requests
- [Core] Fix bug causing Debt.isConfirmed() to sometimes return false when
  not supposed to
[Android] Add menu bar
[Android] Add activity for creating new debt
[Android] Add activity for listing friends
[Android] Add help message when listing zero debts
[Android] Also list pending friend requests (both ways)
[Server] Load pending friend requests for both users
[Console] Stop listing outgoing friend requests
[Android] Friend requests can now be accepted/declined