buffet: Device registration accepts "description", "location" and "display_name".

This values provided by device client by privet API.

BUG=chromium:435687
TEST=unittests

Change-Id: I47ce4a932739c27a3b8dc23f8ec404e9814c3eeb
Reviewed-on: https://chromium-review.googlesource.com/231437
Reviewed-by: Anton Muhin <antonm@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
Tested-by: Vitaly Buka <vitalybuka@chromium.org>