Editor: Fix Notify changed for tilescollection.

git-tfs-id: [https://tfs.codeplex.com:443/tfs/TFS15]$/Atomix;C40732
Editor: Make naming same for events in tiles collection.

git-tfs-id: [https://tfs.codeplex.com:443/tfs/TFS15]$/Atomix;C40733
Editor: Mvvm base, rename OnPropertyChanged.

git-tfs-id: [https://tfs.codeplex.com:443/tfs/TFS15]$/Atomix;C40734