Move VariantType to VariantType.py

Less circular dependencies for imports.

cura/Machines/VariantType.py

@@ -0,0 +1,15 @@
+# Copyright (c) 2018 Ultimaker B.V.
+# Cura is released under the terms of the LGPLv3 or higher.
+
+from enum import Enum
+
+
+class VariantType(Enum):
+    BUILD_PLATE = "buildplate"
+    NOZZLE = "nozzle"
+
+
+ALL_VARIANT_TYPES = (VariantType.BUILD_PLATE, VariantType.NOZZLE)
+
+
+__all__ = ["VariantType", "ALL_VARIANT_TYPES"]