[grenoble] nessie - Add new nessie cluster

data/grid5000/accesses/refrepo.json

data/grid5000/sites/grenoble/clusters/nessie/nessie.json

...id5000/sites/grenoble/clusters/nessie/nodes/nessie-1.json

data/grid5000/sites/grenoble/network_equipments/gw.json

...sites/grenoble/network_equipments/imag-1b-F3-prod-01.json

input/grid5000/disks.yaml

input/grid5000/ipv4.yaml

input/grid5000/sites/grenoble/clusters/nessie/nessie.yaml

...id5000/sites/grenoble/clusters/nessie/nodes/nessie-1.yaml

input/grid5000/sites/grenoble/networks/gw-grenoble.yaml

.../grid5000/sites/grenoble/networks/imag-1b-F3-prod-01.yaml

lib/refrepo/input_loader.rb

lib/refrepo/net_names_mapping.yaml

lib/refrepo/valid/network.rb