Fold up the `SSH' branch of the treeview by default; it's getting

Fold up the `SSH' branch of the treeview by default; it's getting
quite big and tends to hide the existence of the `Serial' config
panel.

This is implemented by folding up every branch of depth 2 or more,
which with any luck might turn out to be general enough to carry
over unchanged if other branches start expanding. Then again, we may
have to fiddle with it again when that time comes; who knows?

[originally from svn r7117]