GROOVIE: T11H: Implement support for spooky animation mode

[antoniou79]

The original game has an option for "spooky" animation mode which as far as I can tell amounts to rendering animations (walking around the house, some GUI elements) in the game with a greyscale palette.

Not everything is in greyscale. The movies --the intro movie, from the weather report and after, and the segments when solving puzzles-- are still in-color. The cursor animated icons are in-color. The puzzle related parts (when in puzzle-mode) are in-color. And the text when saving or loading a game is red and yellow.

This mode also, from what I recall from when playing the game back in the '90s, was far less taxing on the PC hardware so it ran much better on a low end PC (for the game's requirements which were quite demanding).

I am attaching screenshots from this greyscale "spooky" mode.