[GRASS5] Updated extensions for GEM

[benducke at compuserve.de]

I have updated all extensions on my homepage to make
sure they work with 6.1.cvs.

http://www.uni-kiel.de/ufg/ufg_BerDucke.htm

If you want to try GEM on a current version of GRASS,
install the RasterTools extension.
As a proof of concept, I have migrated a bunch of
free-floating add-ons from the GRASS Wiki pages
to this extension. It took me under an hour to get
everything packaged.
This extension is also the first one to sport menu entries
for Michael's new gis.m

Best, Benjamin