Mail Infrastructure Policy

The mail infrastructure policy uses the common mail infrastructure
terminology for its attributes, and provides a common interface for mail
related infrastructure to use SELinux.
Create mta wrapper

Also temporarily rename the mta policy (instead of removing it) so we
can consult it during development of the new mail infrastructure policy.
Fix postfix - Add local as MDA
Fix postfix - Add smtpd as MTA
Mark sysadm as a mail_role capable userdomain