Player Movement Implementation with StartAction/StopAction Events

[jhparkt]

• Implement player movement in 3d space using StartAction/StopAction Events.
• This movement is integrated with the camera, so it can act as the "player."
• The speed, gravity coefficients can be modified in include/server/constants.hpp.
• The hardcoded "room" in the server.cpp file has been modified to render as scaled cubes.

Arrow keys to move.
Space bar to jump.
Left Shift to sprint.
Mouse to look around.

• Currently, pressing left, then pressing right would make the player stop.