Default to using system font

[csmith]

The textpane (and everything else?) currently defaults to using Dialog.

We should default to using the system-wide default font and size.

[greboid]

As far as I remember Dialog is the fall back when I can't locate a system font, I remember adding the code to do this. I'll take a better look later with an IDE but it does look like it's gone missing as I can't see it in UIUtilities anymore.