Include all subnet types; refactoring to add constants for known types
WIP: first iteration of NetworkQuery class

So far all this includes is a method to return an interface for a given
host and subnet type. This will need to be expanded for util methods
to return IP addr, network, interface name, etc. In addition,
we'll need helpers around returning controller IPs, etc.
a few fixes based on review feedback
Retun hash instead of host/interface objects for consistency
warn if we're deleting old subnet_type mappings on db:seed
Merge pull request #281 from sseago/subnet-types

Subnet types