add channels_ssh_pattern and make ssh_pattern and channels_ssh_pattern interpolable

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

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

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

input/grid5000/sites/toulouse/networks/gw.yaml

lib/refrepo/gen/puppet/kavlanngg5k.rb

...efrepo/valid/input/schemas/schema-network_equipments.yaml