shill: First step for rtnl code -- device discovery

Add device_info object and add it to the manager.  Once started,
this will perform rtnl enumeration.  Current tests just assert
that each enumeration completes successfully, but since our code
does not yet store any information based on what it sees, this
cannot be tested yet.

BUG=chromium-os:12933
TEST=New unit tests added

Change-Id: Ie1958222d9831c6117d0ace127857340a11b0bb1
Reviewed-on: http://gerrit.chromium.org/gerrit/655
Reviewed-by: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
diff --git a/shill_daemon.h b/shill_daemon.h
index 1ed3f47..9ccf841 100644
--- a/shill_daemon.h
+++ b/shill_daemon.h
@@ -20,6 +20,7 @@
  public:
   explicit Daemon(Config *config, ControlInterface *control);
   ~Daemon();
+  void Start();
   void Run();
 
  private: