Fix issue #63
Add Michael's textures to the Content project.
Load the new textures.

Launcher.cs is such a mess now, though. Also, the platform's texture
is chosen based on its size.
Load textures for breakable platforms.

The breakable platforms are gray versions of the normal platforms.
Change the platform textures used in the toolbox.
Add comments.
Change the treasure object from a star to a coin.
Reorganize the Texture folder.

In the process, the New Texture folder was removed.
Fix the third How to Play page.
Add an alpha layer to treasure.png.
Modify the image used for page 4 of the How to Play series.

The version being used in the game has the white background, but I left
the version with the background in it in case the majority prefers that
instead.
Change the background used during gameplay.
Add all the new files to the Content project.
Change the textures used in the third page of How to Play.
Add new art assets to Setup project.