GUI contents now hidable, and pane overlays

The GUI pane will now overlay,
and then retract, if it's opened without
using the 'open' button.
This is to allow fast access to options.

GUI panes now also collapse, when you click
on the header.
removed dead code, the 'SWATCHES' sub-header

There was a sub header, labelled 'SWATCHES',
which was in the previous version of SkyBrush.

For some reason it was still being created, and
it has now been removed.