Add wireless connectable interface

libnymea/interfaces/interfaces.qrc

@@ -63,6 +63,7 @@
         <file>noisesensor.json</file>
         <file>co2sensor.json</file>
         <file>presencesensor.json</file>
+        <file>wirelessconnectable.json</file>
     </qresource>
     <qresource prefix="/"/>
 </RCC>

libnymea/interfaces/wirelessconnectable.json

@@ -0,0 +1,14 @@
+{
+    "description": "This interface should be used for device which have the signal strength available. If the signal is to weak, the thing is not connected any more.",
+    "extends": "connectable",
+    "states": [
+        {
+            "name": "signalStrength",
+            "type": "int",
+            "unit": "Percentage",
+            "minValue": 0,
+            "maxValue": 100,
+            "defaultValue": 0
+        }
+    ]
+}