Add support for network.routes

Network routes will iterate over each defined route for an interface name and will build a static route file for that interface.
```yml
eth0:
  network.routes:
    - secure_network:
      ipaddr: 10.2.0.0
      netmask: 255.255.255.0
      gateway: 10.2.0.1
    - HQ_network:
      ipaddr: 10.100.0.0
      netmask: 255.255.0.0
      gateway: 10.100.0.10
```