imp folder prefix

[Egan]

At then end of IMP_tree::init() there is some code to automatically
expand the first level under a folder prefix.

The effect of this is to show the folder prefix as a folder itself, in
the list of folders presented to the user, along with all the folders
it contains, one level beneath it.

This is contrary to the purpose of using a prefix: to hide the prefix
level from the user.

Clearly, the first level under the prefix should be automatically
expanded, as the code does already.  But the entire first level under
the prefix should be shifted up one level, because it *is* the top
level you want the user to see (since you specified a folder prefix),
and the prefix itself should be hidden.

I'm still studying how to patch this.  Any thoughts on how to proceed?

Egan