Overhaul the UI

There have been some rather large (yet subtle) changes to the core UI
in this commit.  The open dialog has been changed to a JFileChooser with
custom filtering and icon code, so that sketch folders now display as
a single file with a UECIDE icon - no more browsing to the sketch folder
and then finding the .ino file within it.  Much cleaner.

Also the Look-And-Feel system has been completely rewritten.  You now have
the ability to select your look and feel (with sensible defaults on a per-
operating system basis).  Coupled with that we have now provided a selection
of extra Look-And-Feel archives to select from (some work better on some
systems than others).  We have the JTattoo collection, which gives lots of
very high-quality themes, plus the Liquid KDE theme.  A preferences drop
down list selector has been provided to select the theme you want, and the
theme changes while you're selecting it, so you can see exactly what you'll
get with any one theme.