NIOSMTP: should implement escaping

### Expected behavior

NIOSMTP's should escape things like names and the body of an email so you can send anything without errors.

### Actual behavior

Nothing is escaped, for example putting an line just containing a full stop (`.`) in an email will cause an SMTP protocol error. The emails should be properly MIME encoded instead.

### Steps to reproduce

Try to send an email with NIOSMTP containing a line with just a full stop.

Start by locating the NIOSMTP message-building and sending entry points, then reproduce the failure with a line containing only a full stop. Trace how names and the email body are emitted and compare the required MIME and SMTP escaping behavior. Done means such messages send successfully without SMTP protocol errors, with coverage for the reproduced case.

Written by the indexing model from the issue text.