Starting a new branch for a speed controller

  - working to get a few things out of concept phase in controls
    theory into simple working examples.  Want to take a simple
    hobby motor which has a 1st order response and add some poles
    to the transfer function to give more options for overshoot
    and other other interesting repsonses.
implemented a PID speed controller

  - I'm calling it PID, but D doesn't work.
  _ P and I are working...kind of, but I need to pull them a little
    closer to what experience recommends for comuting the final control
    effort.
  - However, I'm glad to have the system compiling and a real motor
    working under its control
Several changes

  - Worked to improve PID controller.  Should probably look to
    bring filter into Glow Worm so i can use it as a tool in the
    derivative.
  - Simple plant and control effort changed to use a long for
    u since it often exceeds 32000 when max RPM is around 10K.
  - Most importantly, quadrature was fixed to allows configuration
    for Uno or Due boards.
working to bring Alfred into the new framework
using const Cmd_vel_msgs intead of a struct
Added light_plant to the framework

  - Added light_plant.h to blocks
  - Added cmd_led.h to messages.  Controllers should publish
  cmd_led.h to set the light plant.
several changes

  - Changed State namespace to Led_state in order to be more
  specific.  This required multiple changes throughout the
  clearinghouse.h file to use the new namespace declaration.
cleaned up messages and bumper_plant.h
Added blocks/scanner.h Yahoogit add --all! big day
troubleshooting light plant with whisers in Alfred
Fixed bug with scanner.h\n\n\tadded a clear_distance when the first scan gets constructed.
Three changes

  - Put more text into Flash memory to reduce dynamic memory usage.
  - Added, and then commented out a technique to inspect all messages
    created system wide.  See comments under global variables.
  - Added a build note about temp creation of Message class objects
    when a system uses const Cmd_velocity_msg's.
minor mods to clean up a few print functions
messages for position bot
Merge pull request #2 from zacsketches/position

Position