Explore TK dump to file features to create tournament replay videos

[otizonaizit]

The current situation is not sustainable:
#524 (comment)

[Debilski]

Alternatively, if Tk gets too nasty for pngs, we could make the Qt viewer look similar (and add the missing features) to the Tk and just use this for the pngs. There it is already implemented (#460). Of course we would have to optionally also ship the Qt viewer then.
Or, we use matplotlib (or similar) to create pngs; this could also be nice within Jupyter notebooks.

[Debilski]

FWIW, Canvas.postscript() does indeed yield better results than the ugly anaconda implementation of Tk. Now we just need to attach the headers.

[otizonaizit]

This is done in #542