Font2DTest demo needs to use FontPanel resolution matching the screen

Font2DTest creates a BufferedImage to use as its FontPanel
and then draws to it.
In the current hi-dpi implementation for windows this may result
in a 1.25 scale up of the image to the swing backbuffer and
the results are to say the least awful.
The same effect can be seen to a lesser degree on OS X if
you have a retina display. It does not look so bad but it is clearly
low-res text, not retna scale text.

The fix is to not use a BufferedImage to back the display which
seems likely to have been done mainly for performance, so as
to not have to redraw.
Instead we should draw directly to the Swing backbuffer.