Added MachineManagerModel to Cura

CURA-1278

cura/MachineManagerModel.py

@@ -0,0 +1,25 @@
+
+from PyQt5.QtCore import QObject, pyqtSlot, pyqtProperty, pyqtSignal
+from UM.Application import Application
+from UM.Signal import Signal, signalemitter
+
+class MachineManagerModel(QObject):
+    def __init__(self, parent = None):
+        super().__init__(parent)
+        Application.getInstance().globalContainerStackChanged.connect(self._onGlobalContainerChanged)
+
+    globalContainerChanged = pyqtSignal()
+
+    def _onGlobalContainerChanged(self):
+        self.globalContainerChanged.emit()
+
+    @pyqtSlot(str)
+    def setActiveMachine(self, stack_id):
+        pass
+
+    @pyqtProperty(str, notify = globalContainerChanged)
+    def activeMachineId(self):
+        return Application.getInstance().getGlobalContainerStack().getId()
+
+def createMachineManagerModel(engine, script_engine):
+    return MachineManagerModel()