[nancy][grappe] Add basic power monitoring

.../grid5000/sites/nancy/clusters/grappe/nodes/grappe-1.json

...grid5000/sites/nancy/clusters/grappe/nodes/grappe-10.json

...grid5000/sites/nancy/clusters/grappe/nodes/grappe-11.json

...grid5000/sites/nancy/clusters/grappe/nodes/grappe-12.json

...grid5000/sites/nancy/clusters/grappe/nodes/grappe-13.json

...grid5000/sites/nancy/clusters/grappe/nodes/grappe-14.json

...grid5000/sites/nancy/clusters/grappe/nodes/grappe-15.json

...grid5000/sites/nancy/clusters/grappe/nodes/grappe-16.json

.../grid5000/sites/nancy/clusters/grappe/nodes/grappe-2.json

.../grid5000/sites/nancy/clusters/grappe/nodes/grappe-3.json

.../grid5000/sites/nancy/clusters/grappe/nodes/grappe-4.json

.../grid5000/sites/nancy/clusters/grappe/nodes/grappe-5.json

.../grid5000/sites/nancy/clusters/grappe/nodes/grappe-6.json

.../grid5000/sites/nancy/clusters/grappe/nodes/grappe-7.json

.../grid5000/sites/nancy/clusters/grappe/nodes/grappe-8.json

.../grid5000/sites/nancy/clusters/grappe/nodes/grappe-9.json

data/grid5000/sites/nancy/pdus/grappe-pdu1.json

data/grid5000/sites/nancy/pdus/grappe-pdu2.json

input/grid5000/sites/nancy/clusters/grappe/grappe.yaml

input/grid5000/sites/nancy/clusters/grappe/grappe_pdu.yaml