smbprovider: Implement DBus service for smbprovider with read-only
navigation

Initial CL for SmbProvider that implements the DBus service and contains
Mount, Unmount, ReadDirectory, and GetMetadata. This will be the first
of the CLs that will provide read-only navigation of an SMB share.

BUG=chromium:757625
TEST=Daemon runs, unit tests run fine
CQ-DEPEND=CL:744992
Change-Id: I799651470146d7be3ec3b31a343639a1debf700e
Reviewed-on: https://chromium-review.googlesource.com/625074
Commit-Ready: Zentaro Kavanagh <zentaro@google.com>
Tested-by: Zentaro Kavanagh <zentaro@google.com>
Reviewed-by: Zentaro Kavanagh <zentaro@google.com>
20 files changed