Add Tk overlay: Bot paths

[Debilski]

Show the path that the bots took in a Tk overlay.

I think it could be useful when trying to look at the bots history in UI but to do it properly, it will need some thinking.

Questions/ideas:

• How will we show going back and forth between cells
• How to arrange the lines when multiple bots move over the same cell (I think each bot should have its line in a certain region of the cell so that they don’t conflict)
• Can bot lines be switched on and off individually?
• Should old ones be shown after respawn?
• Ticks for every 10th or 50th move should be shown
• Events like eating and killing should be shown, ideally of course with interacting lines (I realise now that interacting lines imply that old history does not get deleted after respawn)

Surely someone with too much time and graphic skill will be willing to implement this :)