Spirals: make it possible to get the original spirals again

The user just has to Shift+Click File>Open Samples>Spirals and set the
'useOnlyRedAndGreen' variable to false, then Run>Run.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Make File>Open Samples>Spirals green/blue when Alt is pressed

... rather than making this a programmers-only feature...

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>