CURA-4552 Add flavors to GCodeReader. The preRead looks for the flavor

in the GCode and then the right flavor handler is responsible for
reading the code. At this moment just the Griffin and RepRap flavors are
taken into account.

plugins/GCodeReader/RepRapFlavor.py

@@ -0,0 +1,31 @@
+# Copyright (c) 2017 Ultimaker B.V.
+# Cura is released under the terms of the LGPLv3 or higher.
+
+from . import GCodeFlavor
+
+class RepRapFlavor(GCodeFlavor.GCodeFlavor):
+
+    def __init__(self):
+        super().__init__()
+
+    def processMCode(self, M, line, position, path):
+        if M == 82:
+            # Set absolute extrusion mode
+            self._is_absolute_extrusion = True
+        elif M == 83:
+            # Set relative extrusion mode
+            self._is_absolute_extrusion = False
+
+    ##  Set the absolute positioning
+    #   RepRapFlavor code G90 sets position of X, Y, Z, and E to absolute
+    def _gCode90(self, position, params, path):
+        self._is_absolute_positioning = True
+        self._is_absolute_extrusion = True
+        return position
+
+    ##  Set the relative positioning
+    #   RepRapFlavor code G91 sets position of X, Y, Z to relative
+    #   For relative E, M83 is used
+    def _gCode91(self, position, params, path):
+        self._is_absolute_positioning = False
+        return position