Tree view of labels + hiding labels in Web interface + alias labels

[Erik Proper]

1) Due to IMAP usage, you end up with labels such as:
"Apple Mail To Do" and "Deleted Messages"
It would really be helpful if we would be able to hide some of this
"IMAP client created" labels from the web interface

2) In some cases, such as "Deleted Messages" it would be sensible to
define these as aliases to existing labels (i.c. Trash). Mail clients
such as Apple's Mail cannot be told to use Trash as their Deleted
Messages folder, so when using IMAP to access GMail, they will just
create such a folder/label.

3) When creating IMAP folders (on gmail), this leads to labels in
GMail. That's clear. But when I create nested folders, I end up with
label names such as:
- News/Research/Conferences
- News/Research/ACM
- News/Networks/Plaxo
- News/Networks/LinkedIn
which is still not too bad. But, in the webinterface this leads to a
long list of labels which don't fit in the tiny window. It would be
nice to have some kind of tree view for this:
- News
+Networks
- Research
ACM
Plaxo

Cheers,
Erik