Added fields to converted sampletypes.

Cleaned up implementation of Update method of YawRateController.

Made call signature of Updated method of RearWheel match that of
YawRateController.

Added code to compute rear wheel torque constant.
Merged plot_fixes from oliverlee/plot_fixes
Bugfix in YawRateController.  Added plots of debug vars.

Steer torque at previous time step was not being used when performing state
update.
Fixed steer angle plot.
Fixes to speed lookup.
Added test converted data.
Fix for plot_data.py script.

Use script directory instead of current directory.
Fix plot for system state flags.