Polaris server installation

This merge request describe the newly installed Polaris server at Lyon. This server will become the new NFS of Lyon.

Also, this merge request remove retired servers, such as Mizar, Nebula and cyrrus.

data/grid5000/sites/lyon/servers/mizar.json

-{
-  "alias": null,
-  "kind": "physical",
-  "network_adapters": {
-    "bmc": {
-      "ip": "172.17.62.6"
-    },
-    "default": {
-      "ip": "172.16.63.6"
-    }
-  },
-  "serial": null,
-  "type": "server",
-  "uid": "mizar",
-  "warranty": "2010-01"
-}
\ No newline at end of file