Refactored the config models so they they function are more stand alone units.

The seperation of concern got a bit mixed up, as the printer output model was connecting the signals that the config model needed to function together.
With these changes it's now also possible to use the config model as a part of a printjob, since printjobs can also have a configuration

cura/PrinterOutput/ExtruderConfigurationModel.py

@@ -1,8 +1,11 @@
 # Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
+from typing import Optional
 
 from PyQt5.QtCore import pyqtProperty, QObject, pyqtSignal
 
+from cura.PrinterOutput.MaterialOutputModel import MaterialOutputModel
+
 
 class ExtruderConfigurationModel(QObject):
 
@@ -10,38 +13,42 @@ class ExtruderConfigurationModel(QObject):
 
     def __init__(self):
         super().__init__()
-        self._position = -1
-        self._material = None
-        self._hotend_id = None
+        self._position = -1  # type: int
+        self._material = None  # type: Optional[MaterialOutputModel]
+        self._hotend_id = None  # type: Optional[str]
 
-    def setPosition(self, position):
+    def setPosition(self, position: int) -> None:
         self._position = position
 
     @pyqtProperty(int, fset = setPosition, notify = extruderConfigurationChanged)
-    def position(self):
+    def position(self) -> int:
         return self._position
 
-    def setMaterial(self, material):
-        self._material = material
+    def setMaterial(self, material: Optional[MaterialOutputModel]):
+        if self._hotend_id != material:
+            self._material = material
+            self.extruderConfigurationChanged.emit()
 
     @pyqtProperty(QObject, fset = setMaterial, notify = extruderConfigurationChanged)
-    def material(self):
+    def material(self) -> MaterialOutputModel:
         return self._material
 
-    def setHotendID(self, hotend_id):
-        self._hotend_id = hotend_id
+    def setHotendID(self, hotend_id: Optional[str]) -> None:
+        if self._hotend_id != hotend_id:
+            self._hotend_id = hotend_id
+            self.extruderConfigurationChanged.emit()
 
     @pyqtProperty(str, fset = setHotendID, notify = extruderConfigurationChanged)
-    def hotendID(self):
+    def hotendID(self) -> Optional[str]:
         return self._hotend_id
 
     ##  This method is intended to indicate whether the configuration is valid or not.
     #   The method checks if the mandatory fields are or not set
     #   At this moment is always valid since we allow to have empty material and variants.
-    def isValid(self):
+    def isValid(self) -> bool:
         return True
 
-    def __str__(self):
+    def __str__(self) -> str:
         message_chunks = []
         message_chunks.append("Position: " + str(self._position))
         message_chunks.append("-")
@@ -50,7 +57,7 @@ class ExtruderConfigurationModel(QObject):
         message_chunks.append("HotendID: " + self.hotendID if self.hotendID else "empty")
         return " ".join(message_chunks)
 
-    def __eq__(self, other):
+    def __eq__(self, other) -> bool:
         return hash(self) == hash(other)
 
     #   Calculating a hash function using the position of the extruder, the material GUID and the hotend id to check if is