Rename the GtkWindow app to window

It would be hard to choose a more confusing name for a window.
Simplify usage of container widgets
Add control buttons to the window
Remove Hint and Undo from the app menu

These live in the window now
Leave new game action enabled at all times
Disable hint button after it is used

You can only get one hint per turn, so no sense in letting the player
press the button multiple times.
Remove Enable Animations preference
Remove glass marbles theme
Improve the window title of the preferences dialog
Remove old commented code