Add DIP switch support

"-S" option shows DIP switch setting via invoking
onrisc_get_dips() routine.
led option (-l) parsing fix
LEDs: fix sscanf warnings
DIP: free GPIOs at once
LEDs: rework LED init and clean up
LEDs: restore LEDs when counter expired
cli: add an option to blink a LED
LEDs: add destructor routine
LEDs: make GPIO related variables explicitly invalid
cli: provide additional blinking pattern
Documentation: add installation instructions
Bump version to 1.2.0