[X2go-Dev] 3.99 Testing - Clean up of old installations

[John A. Sullivan III]

It does not seem that we do a good job of cleaning up after ourselves in
Windows after uninstalling. Perhaps this is intentional but I would
think we should at least give an option for complete removal.

While working on the packing problem, I scoured through file system and
registry to ensure I had cleaned everything.  The ~/.x2go directory
remained in place after uninstalling.  We also left the registry entries
in place.

I also noticed there were Cygwin entries in the registry. I do not know
if these were left over from the 3.0.1-4 installation or from Pyhoca.
We do not want to delete them if there is an independent Cygwin
installation but, if the only one is the one installed by an old
x2goclient, I would think we should remove references to it in the
registry - John