Add position_sensor_sim class.

This currently contains a class capable of simulating an
indexed encoder and a potentiometer with gaussian noise.

This is mostly Philipp's code, with some modifications by me.

Change-Id: I77925f51916934de02eed24f0de8d6ab51626ba2
diff --git a/frc971/control_loops/control_loops.gyp b/frc971/control_loops/control_loops.gyp
index 1976850..6e882e1 100644
--- a/frc971/control_loops/control_loops.gyp
+++ b/frc971/control_loops/control_loops.gyp
@@ -36,6 +36,24 @@
       'includes': ['../../aos/build/queues.gypi'],
     },
     {
+      'target_name': 'position_sensor_sim',
+      'type': 'static_library',
+      'sources': [
+        'position_sensor_sim.cc',
+      ],
+      'dependencies': [
+        'queues',
+        'gaussian_noise',
+      ],
+    },
+    {
+      'target_name': 'gaussian_noise',
+      'type': 'static_library',
+      'sources': [
+        'gaussian_noise.cc',
+      ],
+    },
+    {
       'target_name': 'coerce_goal',
       'type': 'static_library',
       'sources': [