feat(interfaces): Adding support for interfaces file

This adds the ability for cloudinit to parse a debian interfaces
file and generate the coresponding networkd configs. This still
needs a lot of work to support more configuration options.
feat(cloud-drive): Adding support for reading user-data from cloud-drive

The -cloud-drive flag tells cloudinit to read the user-data from
within the cloud-drive (./openstack/latest/user-data).
refactor(userdata): Moving userdata processing into a function
feat(convertNetconf): Adding support for network config conversion

Adding the flag -convertNetconf which is used to specify the config
format to convert from (right now, only 'debian' is supported).
Once the network configs are generated, they are written to
systemd's runtime network directory and the network is restarted.
feat(systemd): Updating the systemd unit files to use configdrive

This makes it so that /media/configdrive can be used for user-data
and network configs.