Updates Mac Address port return format
Merge pull request #165 from Cerberus98/mac_address_fix

Updates Mac Address port return format
First cut of modular network plugins

Adds the network plugin concept to quark, as well as a new "bridge"
column to the port model for dual mode networking support. Also bumps
the test coverage back up to 90%.
Merge pull request #166 from Cerberus98/default_nets_merge

First cut of modular network plugins