IMAP: Add [TEXT] in response to BODY[TEXT]

In response to BODY[TEXT] we would only send BODY <string>, not the
correct BODY[TEXT] <string>
Check response to IMAP fetch with BODY.PEEK[TEXT]
IMAP: Don't add [HEADER] to RFC822.HEADER response
IMAP: Add unit tests for parts of the log from bug 6022
Merge remote-tracking branch 'zidel/imap'
Update changelog
Release 23 (0.2.4)