Merge PR #539: Add phaseCount state to electricvehicle interface

libnymea/interfaces/electricvehicle.json

@@ -14,6 +14,13 @@
             "minValue": 6,
             "maxValue": 16,
             "optional": true
+        },
+        {
+            "name": "phaseCount",
+            "type": "uint",
+            "minValue": 1,
+            "maxValue": 3,
+            "optional": true
         }
     ]
 }