nfc: Add D-Bus client for NFC Manager.

Added D-Bus client code for the NFC Manager interface.

BUG=305386
TEST=1. chromeos_unittests
     2. Build for Linux with "chromeos=1", check logs to make sure
        that fake device gets added.
     3. Build for Chrome OS. Repeatedly insert and remove USB NFC adapter
        dongle to make sure that the "AdapterAdded" and "AdapterRemoved"
        signals are received from neard by looking at the logs.

R=keybuk@chromium.org, stevenjb@chromium.org

Review URL: https://codereview.chromium.org/26871005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230169 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230169