Moved view stuff to View namespace.

Added OpenCloseChildWindowBehavior which seems like a nice way of separating view/viewmodel concerns. To add a command for opening a new child window:
1) Add the window user control (see View.ColorPicker).
2) Add the DelegateCommand (see ViewModel.SingleTile).
3) In the view from which the window will be opened, add the OpenCloseChildWindowBehavior (see View.SingleTileControl).
4) Add Command binding to relevant element (see TileColor element in View.SingleTileControl).

Added bindings in SingleTileControl for color picker window.
Note: Should modify color picker window to keep a list of "used" colors to make matching an edge color to an existing color simple. Better positioning would be nice too.