Add a LayerData class and a Job class to create it from a Protobuf message

LayerData.py

@@ -0,0 +1,45 @@
+from UM.Mesh.MeshData import MeshData
+
+import numpy
+import math
+
+class LayerData(MeshData):
+    def __init__(self):
+        super().__init__()
+        self._layers = {}
+
+    def addPolygon(self, layer, type, data):
+        if layer not in self._layers:
+            self._layers[layer] = []
+
+        self._layers[layer].append(Polygon(self, type, data))
+
+    def getLayers(self):
+        return self._layers
+
+class Polygon():
+    NoneType = 0
+    Inset0Type = 1
+    InsetXType = 2
+    SkinType = 3
+    SupportType = 4
+    SkirtType = 5
+
+    def __init__(self, mesh, type, data):
+        super().__init__()
+        self._type = type
+        self._begin = mesh._vertex_count
+        mesh.addVertices(data)
+
+        indices = [self._begin + i for i in range(len(data))]
+
+        mesh.addIndices(numpy.array(indices, dtype=numpy.int32))
+        self._end = mesh._vertex_count
+
+    @property
+    def type(self):
+        return self._type
+
+    @property
+    def data(self):
+        return self._data