Bug fix: GameData.clues

Final clue was being ignored when reading in from file because EOF
reached.
Docs: Removed date from todo

It was redundant and too easy to forget to update.
Add: \ui\maingame\clue.py

Working toward functionality of opening a clicked clue.
Add: Clues open upon click. Sound improved.

Game can now pause while waiting for sound to finish. Full clue opens
upon click, but clue opening animation not yet implemented.