Generator: Switch to ViewModel Tiles in handling.

git-tfs-id: [https://tfs.codeplex.com:443/tfs/TFS15]$/Atomix;C40395
Generator: And in main viewmodel too.

git-tfs-id: [https://tfs.codeplex.com:443/tfs/TFS15]$/Atomix;C40396
Generator: Fix tile width/height binding.

git-tfs-id: [https://tfs.codeplex.com:443/tfs/TFS15]$/Atomix;C40397