Changes the game_loop library to a local version

so that I can add whatever event listener I want easily
Panning camera is now easier

After making the game_loop library local and adding the keyUp event
handler, the movement of Camera is better.

Camera continues moving when WASD is pressed, and stops moving as soon
as the WASD keys are released.
The velocity of Camera is scaled when zoomed

Also removes the acceleration phase in the beginning of the camera movement.