[PATCH] Broken help link in IMAP subfolder dialog

[Peter Bloomfield <bloomfld eos ncsu edu>]

- The `Help' button on the IMAP subfolder properties dialog has a bad html
link--this patch fixes it. 
- It also turns the `Browse...' dialog into a 1-click box: selecting a
folder also closes the dialog, as in the message-transfer box, so you don't
need to hit the OK button (and the OK button is correspondingly now a
CANCEL button).
- It also disallows editing the parent_folder input box until an IMAP node
has been selected, to make sure we get the server info. The entry box
should show a visual cue that editing is disallowed (grey box, no cursor,
anything!), but I don't see any way to do that. The entry can be hidden, 
but then the `Browse...' button becomes huge...(sigh)

As always, comments and suggestions welcome!