And edit the command parser (read_handler) accordingly.

It doesn't crash on invalid data for the given object, and returns false in that case, this way we can ignore completely the command containing that invalid data.

Implement the system of confirm/validate turns with the server and other clients. Also implement very simple MOVE and PATH commands to test that it's functionnal. #47

Implement most of the ideas behind the tick + turn system. Clients and server starts and run in a synchronous way. (Huge commit) #47

Also calculate the number of updates to done, each loop turn.
Uses boost::posix_time instead of sf::Time, because we cannot use SFML for the server.

This makes it possible to send a copy of one command to a
list of clients.
Also added a test for that.