Add ability to collapse folders in folder list

[computrav]

I have quite a few folders & subfolders, and it would very handy if they were collapsable and that if the state of them (collapsed or expanded) is persisted between logins. I like being able to easily drag messages to folders to move them, but when the list is very long, I need to scroll down first to make the folder I want visible, then drag the message over. On a related note, if you could make it so that the folder list scrolled vertically when you're in the middle of dragging an email over the folder list, that would be nice too.

[Shane]

please see ticket-> #1267231

[jpingle]

Duplicate of #1267231