Add support for mac address source rules

This is necessary to parse rules generated on OpenStack Havana + Neutron + OpenVSwitch
Making it mergable:

 * Missing type definition
 * Fix failing test
 * Acceptance testing + fix parameter match
 * Renamed mac_addr to mac_source
Merge pull request #337 from damjanek/master

Add support for mac address source rules pt2
Add reference information to firewall module README