Delete ProjectileInfo class
Added placeholder material & texture

Placeholders are useful when no material is available for an object, or
when you  want to see the exact boundaries of the object's quad.
Added Spawn Area material

This material is for debugging purpose only. It will never be seen in
the actual game.
Splitted Globals into Globals & DebuggerGlobals

Globals are used to store general game data, and DebuggerGlobals for
debugging settings.
Changed Unity Settings
Changed graphics for ships and projectiles

Ships texture should point rightward or leftward, depending on it's a
player ship's texture or enemy ship's.
Collision tester now don't test for "Void" anymore.

The game area bounds are now calculated with rectangles instead of
collisions.
Added MotionParameters struct.

This struct is used to store a mobile's motion data :
- Velocity (Vector3)
- Max speed (float)
- Acceleration (float)
- Inertia (float)
- CurrentSpeed (float)
Modified Utils class

To reflect changes in Globals & Debugger Globals.
Modified Gun & Weapon

Gun now shoots a projectile instance, that behaves like any other
mobile.
Projectile class is not abstract anymore.
Added physical motion to Mobile
Added public variables to EventHorizon

- USE_PLACEHOLDER : Tells the game to replace every mobile's material by
the PLACEHOLDER material.
- STARTING_POSITION : the starting position of the player's ship at the
beginning of the level.

InitializeAreaRects() takes the bounds of the 2 Areas (GameArea,
SpawnArea) to compute their Rect and put them in Globals.
Ship.FirePrimary() now takes parameter(s)

The method FirePrimary() now needs the starting position of the
projectile. Generally it's the ship shooting the projectile.
The player ship now stays in the game area.
Put Player class in namespace EventHorizonGame