Expose networks metadata (flags) from Nailgun to UI

Network configuration is exposed now from Nailgun through API on GET requests to
/clusters/#id/network_configuration/neutron/
/clusters/#id/network_configuration/nova_network/
It contains list of dictionaries, one dictionary for every network, where current network parameters are collected.
Metadata from fixtures must be added to the dictionary for every network within the "meta" field.
This will allow UI to deal with networks on the base of their meta instead of names.