[Feature request] Solve statistics

[mooomooo]

At the least, keep a running tally of dates vs solve times (and hinted boxes) by puzzle source, with export to csv or something. Additional fancy features could be number of filled in / correctly filled in boxes vs time per puzzle, some on-screen summary or graph displays, and maybe a high score / fastest solve table.

[yourealwaysbe]

I don't really get much time to implement things unless i'm really motivated, so i probably won't get around to this myself anytime soon. Pull requests welcome :)

Tbh, i've always had my doubts whether i haven't broken the puzzle timing -- it's not something i've tested much, though the numbers don't look obviously wrong.