Demo for input and physics.

Added impulses.
Fixed an issue with the object pool where it wasn't resizing correctly and it wasn't setting the UnitState to None.
Without setting the UnitState to None the pool would never find a correct slot for additional sprites.
Intermediate check-in:

Collisions between objects are working.  Static objects completely stop the spaceship.  However, some oddity in the position of the walls.  top/left/bottom seem to work (although some jaggedness is apparent).  If the demo changes to use the "borders" method instead of walls, then the right wall works perfectly but none of the rest do.

Will investigate later.
Integrated inputphysics branch
Added basic camera zoom, rotation, and follow abilities
Added gamepad support (buttons only for now)
Small performance tweaks
Fixing the NuGet package issue on master
Improvements to the Physics engine.

Collision detection now works with the walls (had some walls outside of bounds in the y-axis).
Player shouldn't tunnel anymore through objects.
Added methods to create a larger assortment of World objects.

Note:  Collisions incorrectly detected on the top and left walls (too early), but not bottom and right.  This leads me to believe that the origin is simply incorrect in the Physics Engine.
Added an XnaGameDebugView so that we can see physics bodies and their interactions.  SpriteWithInputAndPhysics showcases this.
Physics now working as intended =)
Cleaning up old library
Changing .ignore to avoid skipping NuGet dlls in checkin
Merge branch 'master' into inputphysics

Conflicts:
	src/demos/SpriteWithInputAndPhysics/SpriteWithInputAndPhysics/Program.cs
	src/demos/SpriteWithInputAndPhysics/SpriteWithInputAndPhysics/SpriteWithInputAndPhysics.csproj
	src/fwd.Xna/XnaGame.cs
	src/fwd.sln
Cleanup from merge artifacts
Merge branch 'master' of github.com:combitstudios/fwd into animation

Conflicts:
	.gitignore
	src/demos/SplitScreen/SplitScreen/SplitScreen.csproj.Debug.cachefile
	src/fwd.sln