Player entity understands up / down / stop

- we used to pass a vector but the values were duplicated in the different input modules
The device gamepad sends single actions (up / down / stop)

- the bridge will be responsible for sending them continuously (throttled) if needed
- using HTML5 touch events
fix server "match" unit tests
game is playable on keyboard + device, no lag!

- the keyboard & device send "up" or "down" a single time
- the player has no friction, so that's enough to keep it going
- until we send "stop" (on keyup / touched) and the player stops