General advances in Enemy (the parent class), adjustments in Game, Animation, and others.
New sprite for the EnemyBeam.
Minimal changes in some enemies
Full integration of all enemies. New debug mode for testing enemies (press T in the menu, F1..F6 for each type of enemy).
Merge remote-tracking branch 'origin/master' into levelchange

Conflicts:
	IS_XNA_Shooter/IS_XNA_Shooter/IS_XNA_Shooter/GameB.cs
	IS_XNA_Shooter/IS_XNA_Shooter/IS_XNA_Shooter/LevelB.cs