Define device policies for enterpise printers.

Enterprise printers in ChromeOS can be configured either for a user or
for the device.  This implements the device policy which is identical
to the user policy.

Bug: 758679
Change-Id: I05dcb255d1ca50b2c16d94a5540232c313d5d4fe
Reviewed-on: https://chromium-review.googlesource.com/646695
Commit-Queue: Sean Kau <skau@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Drew Wilson <atwilson@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#499371}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: f183a0083e749de3c9a80044deb83a1173fe249b