hookup_moveoff.tcl: new [HAL]HALFILE

New halfile can be added to existing ini configurations to:

  1) disconnect existing motor-pos-cmd and motor-pos-fb pins
  2) load the moveoff component
  3) establish control pin values for the component based on
     ini file settings (or built-in defaults)
  4) reconnect the motor-pos-cmd and motor-pos-fb pins
     routed through the moveoff component.

New sim configurations are provided:
   moveoff_demo4 (same as moveoff_demo2 but uses hookup_moveoff.tcl)
   moveoff_demo5 (same as moveoff_demo3 but uses hookup_moveoff.tcl)
   moveoff_demo6 (same as moveoff_demo2 but uses hookup_moveoff.tcl)

moveoff_demo6 includes [HAL]HALFILE = noshort.hal that separates
the cmd and fb paths to veriy hookup_moveoff.tcl behavior for
servo-like hal connections.

Signed-off-by: Dewey Garrett <dgarrett@panix.com>