moveoff_gui: track enable for external setters

Signed-off-by: Dewey Garrett <dgarrett@panix.com>
moveoff_gui: options for autoresume with delay

External Hal logic can be used to gate off equipment (spindle,
coolant,etc.) using the condition of the halui.program.is_paused
output pin.

With the new options:

  -autoresume -delay delay_secs

The pause interval is extended by delay_secs and then the
halui.program.resume pin is pulsed to resume the program.

This facility can be used when a delay is required to allow
equipment controlled by external logic during a pause
(like a spindle) to come up to speed before program resumption.

usage:
      moveoff_gui -autoresume -delay secs ... other options

+ update README etc
+ some whitespace cleanup
Signed-off-by: Dewey Garrett <dgarrett@panix.com>