Add flexibility for BatchTiledMapRenderer users.

User may provide their own SpriteBatch in the constructor. Also, added
setMap method to allow the map to be changed. This makes sense for
renderers backed by SpriteBatch since nothing about the map is cached in
the renderer.
Change TmxMaploader to an AsynchronousAssetLoader
Clean up GdxTests.gwt.xml a bit

Added FreeTypeDisposeTest to exludes.
Removed several tests that no longer exist.
Changed TileTest so it uses TimeUtils instead of System.nanoTime directly.