Allow fractional font sizes

The maximum and minimum font sizes can only be set as integers but in operation the resize is 120%. So for example if normal font size was 13px the next down would be 10.8333. If I set 11px then the minimum becomes 11px so the next step up is 13.2px. I can never get back to where I started.

The work around is either to set minimum to be the same as normal, assuming that normal is an integer font size which on zero point theme it isn't. Or to make normal a fractional size, e.g 13.2px which if minimum is 11px would allow 1 step down, with step up going back to default size.