Added getters for MachineAction

CURA-1385

cura/MachineAction.py

@@ -7,5 +7,12 @@ from UM.PluginObject import PluginObject
 
 class MachineAction(QObject, PluginObject):
     def __init__(self, key, label = ""):
+        super().__init__()
         self._key = key
         self._label = label
+
+    def getKey(self):
+        return self._key
+
+    def getLabel(self):
+        return self._label