Add 'rake mass:create'

See doc in https://www.grid5000.fr/w/TechTeam:Add_new_cluster

doc/sophia-clusters-mass-create.csv

+site,cluster,node (not used by script),mac_prod,mac_bmc
+sophia,mercantour1,mercantour1-1,e0:db:55:fd:3a:47,e0:db:55:fd:3a:49
+sophia,mercantour1,mercantour1-2,e0:db:55:fd:3a:2f,e0:db:55:fd:3a:31
+sophia,mercantour1,mercantour1-3,e0:db:55:fd:39:96,e0:db:55:fd:39:98
+sophia,mercantour1,mercantour1-4,e0:db:55:fd:39:e7,e0:db:55:fd:39:e9
+sophia,mercantour1,mercantour1-5,e0:db:55:fd:38:5e,e0:db:55:fd:38:60
+sophia,mercantour1,mercantour1-6,e0:db:55:fd:3a:20,e0:db:55:fd:3a:22
+sophia,mercantour1,mercantour1-7,e0:db:55:fd:39:87,e0:db:55:fd:39:89
+sophia,mercantour1,mercantour1-8,e0:db:55:fd:3a:02,e0:db:55:fd:3a:04
+sophia,mercantour1,mercantour1-9,e0:db:55:fd:39:69,e0:db:55:fd:39:6b
+sophia,mercantour1,mercantour1-10,e0:db:55:fd:39:d5,e0:db:55:fd:39:d7
+sophia,mercantour1,mercantour1-11,e0:db:55:fd:38:d9,e0:db:55:fd:38:db
+sophia,mercantour1,mercantour1-12,e0:db:55:fd:38:7f,e0:db:55:fd:38:81
+sophia,mercantour1,mercantour1-13,e0:db:55:fd:2f:d0,e0:db:55:fd:2f:d2
+sophia,mercantour1,mercantour1-14,e0:db:55:fd:39:81,e0:db:55:fd:39:83
+sophia,mercantour1,mercantour1-15,34:17:eb:e7:25:01,34:17:eb:e7:25:03
+sophia,mercantour1,mercantour1-16,e0:db:55:fd:39:ab,e0:db:55:fd:39:ad
+sophia,esterel31,esterel31-1,50:9a:4c:70:fa:7c,f4:02:70:ed:22:5a
+sophia,esterel31,esterel31-2,50:9a:4c:70:aa:e1,f4:02:70:ed:1c:2a
+sophia,esterel31,esterel31-3,50:9a:4c:6c:38:ad,f4:02:70:ed:2a:84
+sophia,esterel31,esterel31-4,50:9a:4c:6c:38:6b,f4:02:70:ed:2e:a4