shill: Cellular device: GetModemStatus and GetModemInfo.

Also, put in place the skeleton for all Start/Enable steps.

BUG=chromium-os:18315
TEST=unit tests, tested on device

Change-Id: If8b5a8ba9bbcfa99f1c6b168bd8307c1578155f7
Reviewed-on: http://gerrit.chromium.org/gerrit/5082
Tested-by: Darin Petkov <petkov@chromium.org>
Reviewed-by: Jason Glasgow <jglasgow@chromium.org>
Reviewed-by: Chris Masone <cmasone@chromium.org>
diff --git a/dbus_properties.h b/dbus_properties.h
index ca22db5..0a290ef 100644
--- a/dbus_properties.h
+++ b/dbus_properties.h
@@ -25,6 +25,10 @@
                         const std::string &key,
                         uint32 *value);
 
+  static bool GetUint16(const DBusPropertiesMap &properties,
+                        const std::string &key,
+                        uint16 *value);
+
  private:
   DISALLOW_COPY_AND_ASSIGN(DBusProperties);
 };