Adding the factory classes for MSA implementations
Composer: use the MSAFactory for object instantiation
Move capability checking for the composer into Model
wip: move the submission logic into an extra file
Composer: proper return value when some parts are not available
wip: switch to event-driven sending of messages

Totally untested, probably doesn't work at all.
wip: unit testing the submission
Submission: progress logging
Don't invoke non-existent slot
Submission: wip tests
Submission: make sure that the actual message body is produced
Submission: saving message to the Sent folder
Submission: improve logging
More tests for saubmission and saving
Submission: moving UID SUBMIT IMAP submission to a MSA implementation, part one
Submission: implement sending via IMAP through a MSA, part two
refactoring: shared code
FakeMSA: user control of the reported capabilities
tests: check that submission is blocked on unavailable file attachments
tests: make sure justKeepTask is not time-sensitive to the pending fetch requests