Add skeletons for the Treasure and Deathtrap classes.
Render treasures.
Make an object's height and width independent of the texture.

I'm not sure that hardcoding the dimensions of objects is a good idea,
but I didn't want the dimensions of an object to depend on the texture
either. Decoupling the two is for the best, I think.

Also, Git yelled at me because the line endings are different or
something, so I had to fix that first...
Remove the Viewport field from the Ball class.

The width and height of the playing field is specified in two
constants in the Simulation class instead.
Minor change to InBounds().
Render death traps.
Updated Physics and Collision

Updated the game to use Farseer Physics engine. The Ball and Platform
classes were modified. The Gamescreen class was completely redone.
Merge branch 'master' into game-mechanics-newarch
Merge branch 'master' into game-mechanics-newarch

Conflicts:
	PuzzlePathDimension/Game1.cs
	PuzzlePathDimensionContent/PuzzlePathDimensionContent.contentproj
Merge branch 'master' into game-mechanics-newarch
Merge branch 'master' into game-mechanics-newarch
Merge branch 'master' into game-mechanics-newarch

Conflicts:
	PuzzlePathDimension/Game1.cs
	PuzzlePathDimension/GameStates/SimulationState.cs
	PuzzlePathDimension/PuzzlePathDimension.csproj
Merge branch 'master' into Brian_Collision-fork

There are still a lot of parts that need to be integrated properly,
but the physics engine works. Here are a few:
- The platforms defined in the XML file did not work well, so
the AddPlatform() method in the LevelLoader class is commented out.
- Similarly, I have the LoadLevel() method also take in a World
parameter, and I'm not sure if that's the best thing to do.
- I probably didn't put the other parts of the former GameScreen class
in the best places either...

Conflicts:
	PuzzlePathDimension/GameScreen.cs
	PuzzlePathDimension/Models/Ball.cs
	PuzzlePathDimensionContent/PuzzlePathDimensionContent.contentproj
Fix platform weirdness.

This commit allows the physics engine to work with all types of
platforms, not just those defined in the original Brian_Collision
branch. This allows the data in the example XML file to be interpreted
properly. The following changes were made:
- The 20x20 texture is now scaled to fit the size of the platform.
- Code has been added to compensate for the fact that the physics
engine treats (width / 2, height / 2) as the position of the platform.
- Due to this, the code that creates the walls was rewritten.
Remove some remnants of the old collision detection.
Add the Farseer source code to the repo.

Also, rewrite some parts of Platform.cs and CreateBox() to be a bit
clearer. The .dll is removed as well.
Possible fix for the assertion failure.

This needs to be tested more. Also, I changed the test level slightly
because it was possible for the ball to go inside the platform.
Allow the ball to be launched with different velocities.
Read in and render treasures and death traps.
Make treasures disappear when touched.