Puzzle variants

Introduce striping and narrowing puzzle variants which substantially change the experience.

Striping puzzle variants will have you hunting for even/odd columns, withering away until that final revelation

Narrowing causes the evidence to shrink inwards until a revelation emerges.

Both are fun variants, and are randomly chosen in addition to the standard variant.

Also:

• Also, we generate less useless vertical negative assertion clues. If they're present, they're much more likely to be meaningful in the solution.
• seed selection dialogue
• restart game
• timer stops when game is finished (rather than counting onwards)
• improved windows installer allows selection to install for all users or just you