Implement moving the player

Player: Add rotation and linear speeds, as well as their current state.
Player: Allow to move in the local coordinates and compute
    world-speed equivalent.
Player: Update movement axis while rotating.

World: Add a function to advance a step.
Main: Handle key events, add world step in the main loop.

Player.h

@@ -17,6 +17,14 @@ public:
     float y;
     float orientation;
 
+    float moveSpeed = 5;
+    float rotationSpeed = 180;
+
+    float currentMoveSpeedX = 0;
+    float currentMoveSpeedY = 0;
+
+    float currentRotationSpeed = 0;
+
     /* View properties. */
     float fov = 70;
     float sensorSize = 0.035; /* 35mm, about equivalent to human eye ? */
@@ -24,6 +32,7 @@ public:
 
     void move(float dx, float dy);
     void rotate(float alpha);
+    void updateSpeed(float localX, float localY);
 };