Reopening 587

Re-fixing encryption

So while I will continue to prefer port 465, in order to support
public-facing port 587, it really is best to enable wrapper mode only
for the appropriate service. In which case, it should be enabled in
`master.cf` NOT `main.cf`.

Also, to better set relay restrictions, I'm fixing `mydestinations` and
adding `relay_domains`.

Fix encryption setup

Configuration was a bit confused on account of running both SMTPD and
Submission ports. I am going to prefer port 465 with implicit TLS, and
to correctly support that mode I am setting wrapper mode on.

sr.ht

Adding a postfix server image.

Adding images for the sr.ht system (meta+todo+git).