Game: Remove dependency on Empty texture.

git-tfs-id: [https://tfs.codeplex.com:443/tfs/TFS15]$/Atomix;C41373
Game: Refactor namespaces.

git-tfs-id: [https://tfs.codeplex.com:443/tfs/TFS15]$/Atomix;C41374
Game: Document MessageBox.

git-tfs-id: [https://tfs.codeplex.com:443/tfs/TFS15]$/Atomix;C41375