Support for pixel fonts

[tomek-szczesny]

Just leaving a note here so we won't forget.
Would be great to fit 6 lines of text on a 9mm tape. :)

[tomek-szczesny]

At this point it is feasible to print 5 lines using Carlito Bold on 9mm or 12mm tape.
It is not ideal, because due to monochrome scaling, in 4-row variant I can't see much difference between "i" and "l".
To fit 5 lines I had to modify size percentage manually in GUI.