system_api: Add new value and protos for authpolicy.

Adds ERROR_CACHE_DEVICE_POLICY: needed to report to Chrome that device
policy cached on authpolicy side.

Adds protos for D-Bus function inputs. Needed to switch D-Bus calls to
protobufs inputs.

BUG=chromium:684679,chromium:782695
TEST=none

Change-Id: I35855edc781ad373007a8ef07e55f1e9f02f9016
Reviewed-on: https://chromium-review.googlesource.com/771630


Commit-Ready: Roman Sorokin <rsorokin@chromium.org>
Tested-by: Roman Sorokin <rsorokin@chromium.org>
Reviewed-by: Lutz Justen <ljusten@chromium.org>
Reviewed-by: Roman Sorokin <rsorokin@chromium.org>