Add MariaDB, DashMachine, DNSRoboCert, Postgres containers.

Added:

• mariadb container.
• dashmachine container.
• postgres container.
• dnsrobocert container.

Changed:

• vimrc updated with better organization, formatting.
• imapsync documentation updated.
• bulk downloader for reddit instructions added.

Removed:

• heimdall container (use dashmachine instead).
• letsencrypt container (superceeded by dnsrobocert).