Collision, Bullets, updated waypoints

Added bullets (very primitive).  Updated collision new Collidable class
that everyone GameObject that should have some collision detects will
have.  The Collision class can check if two collidables are colliding.
Waypoints are now only at corners.  Tower AI needs an update, it is
shooting randomly
Tower Targeting

Added ability to see what a tower is targeting. Can modify this when
placing a tower once UI is in to show during placement and when a tower
is selected in the field.
Camera System

Added the camera system.  Able to zoom in/out and pan around.  Still
needs tweaking with making sure everything is calculating positioning
and rendering in the correct spots.  Need to add culling to speed up
draws. (Collision is there just need to test it)
Refactoring

Changed some camera specs no longer moveable and no more zooming.  Basic
GUI class starting.  TIle Effects start