Add python model for 2019 wrist

Need to tune the mass for real though.

Change-Id: I4e4431f99e1ad19bab97acd097fb8ad32d524019
diff --git a/frc971/control_loops/python/control_loop.py b/frc971/control_loops/python/control_loop.py
index 74cd389..9aa00df 100644
--- a/frc971/control_loops/python/control_loop.py
+++ b/frc971/control_loops/python/control_loop.py
@@ -587,6 +587,8 @@
     self.Kv = (self.free_speed / (12.0 - self.resistance * self.free_current))
     # Torque constant (N * m / A)
     self.Kt = self.stall_torque / self.stall_current
+    # Motor inertia in kg m^2
+    self.motor_inertia = 0.000006
 
 class MN3510(object):
   def __init__(self):