Remove all obsolete clutter code. Upgrade to GTK4.
#13 is partially fixed because button sized are consistent and the players' scores are not hidden by any buttons.
Fixes #15 (closed) & Fixes #54 (closed) because this screen was full of deprecated (since GTK 4.10) objects and has been removed.
Fixes #33 (closed) because data/nibbles.css is deprecated (since GTK 4.10) and had been removed.
Fixes #42 (closed) because the new rendering does it this way.
Fixes #53 (closed) because clutter-gtk has been removed, we now use Cairo to render the view (nibbles-view.vala).
Edited by Ben Corby