Misc improvements

[NightTsarina]

Hi! I have started using this role, and made a few improvements that I think might be useful for the wider community:

• Remove unneeded extra packages
• Update defaults to match current Debian settings
  It also adds the ability to use the 'unix-dgram' service type, which should
  be specificed as 'unix_dgram'.
• Automatically indent multiline args in master.cf
• Properly differenciate between false and falsy values
• Allow controlling the order of config options
• Allow passing lists in postfix_config