Move models around again

- Move machine related models to cura.Machines.Models
 - Move printer device related models to cura.PrinterOutput.Models
 - Other UI/GUI related modules in cura.UI

cura/Machines/Models/BuildPlateModel.py

@@ -0,0 +1,51 @@
+# Copyright (c) 2018 Ultimaker B.V.
+# Cura is released under the terms of the LGPLv3 or higher.
+
+from PyQt5.QtCore import Qt
+
+from UM.Application import Application
+from UM.Logger import Logger
+from UM.Qt.ListModel import ListModel
+from UM.Util import parseBool
+
+from cura.Machines.VariantType import VariantType
+
+
+class BuildPlateModel(ListModel):
+    NameRole = Qt.UserRole + 1
+    ContainerNodeRole = Qt.UserRole + 2
+
+    def __init__(self, parent = None):
+        super().__init__(parent)
+
+        self.addRoleName(self.NameRole, "name")
+        self.addRoleName(self.ContainerNodeRole, "container_node")
+
+        self._application = Application.getInstance()
+        self._variant_manager = self._application._variant_manager
+        self._machine_manager = self._application.getMachineManager()
+
+        self._machine_manager.globalContainerChanged.connect(self._update)
+
+        self._update()
+
+    def _update(self):
+        Logger.log("d", "Updating {model_class_name}.".format(model_class_name = self.__class__.__name__))
+        global_stack = self._machine_manager._global_container_stack
+        if not global_stack:
+            self.setItems([])
+            return
+
+        has_variants = parseBool(global_stack.getMetaDataEntry("has_variant_buildplates", False))
+        if not has_variants:
+            self.setItems([])
+            return
+
+        variant_dict = self._variant_manager.getVariantNodes(global_stack, variant_type = VariantType.BUILD_PLATE)
+
+        item_list = []
+        for name, variant_node in variant_dict.items():
+            item = {"name": name,
+                    "container_node": variant_node}
+            item_list.append(item)
+        self.setItems(item_list)