ref: 0.1.1 aerc/worker/imap d---------
Wait for listing to complete before sending Done
Don't send Done until finished fetching messages
Skip non selectable mailboxes in directory listing

If a MailboxInfo has the attribute \Noselect,
it is not possible to use this name as a selectable mailbox.

Therefore it should not be passed to the directory handlers.
The issue pops up if one has a hierarchy like this:

Even though lists is not a valid inbox (doesn't contain mail, only other maildirs)
it will show up in the directory listing, when we iterate over the MailboxInfo.

It does have the corresponding attribute set though and we can simply filter it out.
Load IMAP worker for imap+insecure
Flesh out multipart switcher
Copy sent emails to the Sent folder

Or rather, to a user-specified folder
Implement :copy (aka :cp)
Handle external message deletions
Handle incoming emails gracefully
worker/imap: use the IMAP connection from a single goroutine

Unfortunately, the IMAP protocol hasn't been designed to be used from multiple
goroutines at the same time. For instance, if you fetch twice the same message
from two different goroutines, it's not possible to tell whether the response
is for one receiver or the other. For this reason, go-imap clients aren't safe
to use from multiple goroutines.

This commit changes the IMAP workers to be synchronous again (a command is
executed only after the previous one has completed). To use IMAP from different
threads, popular clients (e.g. Thunderbird) typically open multiple
Make message viewer real, part two
Rename FetchMessageBodies to FetchFullMessages
Make the message viewer real, part one
Don't parse mail in worker; send a reader instead
Pull BodyStructure up from IMAP worker
Add body fetching support code
Implement :delete-message
Display message subjects in message list
Implement message store side of message fetching