BlackBox: Ability to mark a laser as done.

[Electos4638]

In many puzzles, one can mark a clue as done. In Black Box, right clicking on a laser start point won't mark the laser as done, but mark/unmark its entire row/column as no ball.

Lasers are an important part of the game. It is difficult to remember or write down on a piece of paper whether each laser is satisfied by the ball layout guess. It'd be best to be able to note a laser's satisfaction in game.