Bug 813411 - [email/IMAP] port/import Thunderbird's IMAP and SMTP fake-servers. r=jrburke

Land changes from https://github.com/mozilla-b2g/gaia-email-libs-and-more/pull/224
Merge pull request #11139 from asutherland/email-imap-fakeserver-fixes

Bug 813411 - [email/IMAP] port/import Thunderbird's IMAP and SMTP fake-servers. r=jrburke