Make swing fonts more like Tk fonts

In PyCharm, the turtle graphics support from #152 works pretty well, but the fonts aren't quite the same as the Tk fonts used in Python turtle graphics. See if there's any way to improve them. The SWT fonts used in Eclipse were pretty close to Tk fonts, except the tabs seem to expand in multiples of four x's instead of eight. See what the difference is between font support in Swing and SWT.

If nothing else, see whether font parameters can be adjusted to get closer to Tk fonts.

Review the turtle graphics support from issue #152, then compare the Swing and SWT font behavior with the Tk fonts used by Python turtle graphics. Investigate whether font parameters or tab-width handling can bring Swing closer to Tk; done means a documented or tested improvement in the rendered fonts.

Written by the indexing model from the issue text.