Remove spurious trailing commas

This was a remnant from 41920a18cc2005ba602461e207a08544224b91d3.
Add InputStream/OutputStream and many more changes

- remove some irrelevant fields from api/device dicts

- replace device dicts with plain device IDs in Stream constructor
  and add more arguments (as replacement for dicts)

- change apis() to hostapi_info() and devices() to device_info().
  Both take an optional device ID.

... and several more things.