Adding support for Open vSwitch bridges and ports

Added a few ovs options so that its possible to configure openvswitch with this cookbook.

Here's an example of some interfaces I have made:


```
  network_interfaces 'br-ex' do
    bootproto 'dhcp'
    ovs_type 'OVSBridge'
    ovs_ports 'bond0'
  end

  network_interfaces 'bond0' do
    ovs_type 'OVSBond'
    ovs_bridge 'br-ex'
    ovs_bonds 'em1 em2'
    ovs_options 'bond_mode=active-backup'
  end
```