Initial submission of GNU Mailman 3 into the ports tree. There will be separate ports for the rest of the suite: python client, Postorious, Hyperkitty.
- git snapshot instead of stable 3.1.1; the stable version explicitly requires an older mail/py-aiosmtpd no longer available in the tree
- The use of devel/py-click requires a UTF-8 locale; the rc script reflects this
- This port can also use databases/py-sqlalchemy11 but not databases/py-sqlalchemy12, but the dependency set here is for databases/py-sqlalchemy10 so as to not foul the databases/py-alembic dependency
- Patches deal mainly with path fixes to conform to FreeBSD filesystem structure