--gpio command line

Hi Richard,

I've added --gpio command line parameter to specify GPIO pins, this is handy if Adafruit cobbler is used. I've also added posibility to read current position of a servo, but is has quite limited use as output goes to servod stdout. For a quick and dirty debugging from a terminal it is enough, but for usign in scripts it would be better to replace it with TCP socket and use ncat to send/receive commands. Will add it in future when start debuggin my new project.

Regards,
Andrey