New puzzle: 'Mosaic'.

This is similar in concept to Minesweeper, in that each clue tells you
the number of things (in this case, just 'black squares') in the
surrounding 3x3 grid section.

But unlike Minesweeper, there's no separation between squares that can
contain clues, and squares that can contain the things you're looking
for - a clue square may or may not itself be coloured black, and if
so, its clue counts itself.

So there's also no hidden information: the clues can all be shown up
front, and the difficulty arises from the game generator choosing
which squares to provide clues for at all.

Contributed by a new author, Didi Kohen. Currently only has one
difficulty level, but harder ones would be possible to add later.

.gitignore

@@ -46,6 +46,7 @@ include/
 /matching
 /mines
 /mineobfusc
+/mosaic
 /net
 /netslide
 /nullgame