Add basic UFP writer plug-in

This already implements most of it. Just the thumbnail must still be gotten and put inside the container.

Contributes to issue CURA-4872.

plugins/UFPWriter/UFPWriter.py

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+#Copyright (c) 2018 Ultimaker B.V.
+#Cura is released under the terms of the LGPLv3 or higher.
+
+import charon
+
+from UM.Mesh.MeshWriter import MeshWriter #The writer we need to implement.
+from UM.PluginRegistry import PluginRegistry #To get the g-code writer.
+
+class UFPWriter(MeshWriter):
+    def write(self, stream, nodes, mode = MeshWriter.OutputMode.BinaryMode):
+        archive = charon.VirtualFile()
+        archive.open(stream, charon.OpenMode.WriteOnly)
+
+        #Store the g-code from the scene.
+        archive.addContentType(extension = "gcode", mime_type = "text/x-gcode")
+        gcode = archive.getStream("/3D/model.gcode")
+        PluginRegistry.getInstance().getPluginObject("GCodeWriter").write(gcode, None)
+        archive.addRelation(target = "/3D/model.gcode", file_type = "http://schemas.ultimaker.org/package/2018/relationships/gcode")
+
+        #Store the thumbnail.
+        #TODO

plugins/UFPWriter/__init__.py

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+#Copyright (c) 2018 Ultimaker B.V.
+#Cura is released under the terms of the LGPLv3 or higher.
+
+from . import UFPWriter
+from UM.i18n import i18nCatalog #To translate the file format description.
+from UM.Mesh.MeshWriter import MeshWriter #For the binary mode flag.
+
+i18n_catalog = i18nCatalog("cura")
+
+def getMetaData():
+    return {
+        "mesh_writer": {
+            "output": [
+                {
+                    "mime_type": "application/x-ufp",
+                    "mode": MeshWriter.OutputMode.BinaryMode,
+                    "extension": "ufp",
+                    "description": i18n_catalog.i18nc("@item:inlistbox", "Ultimaker Format Package")
+                }
+            ]
+        }
+    }
+
+def register(app):
+    return { "mesh_writer": UFPWriter.UFPWriter() }

plugins/UFPWriter/plugin.json

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+{
+    "name": "UFP Writer",
+    "author": "Ultimaker B.V.",
+    "version": "1.0.0",
+    "description": "Provides support for writing Ultimaker Format Packages.",
+    "api": 4,
+    "i18n-catalog": "cura"
+}