Switched to new development model.

Created new branch `develop`.
Connection event has been added.

This event was added for network testing.
Merge branch 'connection_event' into develop
Added and tested the connection event.
Added signal handler for correct exit from programm.
Improved Makefile
Fixed Makefile.
Merge branch 'develop-upstream' into develop

Conflicts:
	Makefile
Updated UI image in TODO
TODO: Statistics on players when Tab is pressed
Chaned Makefile. Added skeleton for backends.
Added client's threads scheme in TODO.
Understood what basic network mechanism must be.

Full version of handshaking with client has been written:
- Client connect to the server;
- Other clients recieve notify about it;
- Client recieves MSGTYPE_CONNECT_OK message which means
  that all is all-right.

Also I fixed some functions from cdata.c.
Add disconnect_client, disconnect_server, and disconnect_notify events.

Refactored players_*() funcs and `struct player*`.
Adapted Minoru's ncurses backend and now we have some kind of UI ;^).

Fixed Makefile, now differente files cdata.o are generated for client
and server.
TODO: CLI params parsing in client.c
Added notifications in UI.
Added more notify events in client.
Added a map.

But loading maps from server is not ready yet.
Also I tried to make player's movement, but
has been found that it's not a real time.
In next commit I'll try to fix it.
Movement is smooth now.

Need to think about checking of collisions
on a client side.