Ability to select special folders manually

[danirabbit]

Problem

When adding a Gmail IMAP account, the "Sent" and "Archive" folders aren't set and need to be selected manually afaict. This means that out of the box, the "Archive" functionality doesn't work in Mail because there is no set "Archive" folder

Proposal

Add a page to select special folders when adding an IMAP account. This gives us an opportunity to check that special folders were selected automatically and if they weren't, set them up.

While we're here, this seems like the "Refresh" setting should maybe move to this page so we can separate connection settings from like account settings. But maybe I'm off on this one

Prior Art (Optional)

Evolution has this page for setting special folders: