Magic Cube

Convert TransparentButton to Material Design.

New drawables.

Correct order of the tutorials.

Correct order of the tutorials.

Correct the style.

Convert the theme to be a MaterialTheme and the TransparentImageButton to be a MaterialButton - the first forced by the second, and the second because a MaterialButton gives us control over the location of the icon in top of it. We need that because of the new 'solve/scramble' split-button in the lower right of the Play screen.

Fix the solver (after rearranging the faces of the cuboids)

Fix problems with TwistyObjectNode 'object scale' property.
Now this property is not part of the Node at all, but its initial value passed to the object in its constructor.

Bugfixes for crashes from Firebase.

Bugfix.