Only currently works on SSH1; SSH2 should be doable but it's late
and I have other things to do tonight. The Cool Guy award for this
one goes to Nicolas Barry, for doing most of the work and actually
understanding the code he was adding to.
[originally from svn r1176]
problems: controls are now destroyed and recreated on a panel
switch. In addition, this patch also introduces a better means of
doing the group boxes.
[originally from svn r884]
features (prompt for passphrase twice, prompt before overwriting a
file, check the key file was actually saved OK), testing of the
generated keys to make sure I got the file format right, and support
for a variable key size. I think what's already here is basically
sound though.
[originally from svn r715]
