[uwhdr] Only start up the IO if we can find pigpio.
[uwhdr] Only start up the IO if we can find pigpio.

Otherwise, stub it out.

Navisjon/uwh-display,jroelofs/uwh-display,Navisjon/uwh-display,Navisjon/uwh-display,jroelofs/uwh-display,jroelofs/uwh-display,Navisjon/uwh-display