Updated testing harness and input_set for MG tests and added first MG test: test_mg_basic

tests/test_mg_basic/test_mg_basic.py

@@ -0,0 +1,17 @@
+#!/usr/bin/env python
+
+import os
+import sys
+sys.path.insert(0, os.pardir)
+from testing_harness import TestHarness, PyAPITestHarness
+import openmc
+
+
+class MGBasicTestHarness(PyAPITestHarness):
+    def _build_inputs(self):
+        super(MGBasicTestHarness, self)._build_inputs()
+
+
+if __name__ == '__main__':
+    harness = MGBasicTestHarness('statepoint.10.*', False, mg=True)
+    harness.main()