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/modem_proxy.cc b/modem_proxy.cc
index 9bcf219..cef28a5 100644
--- a/modem_proxy.cc
+++ b/modem_proxy.cc
@@ -21,6 +21,10 @@
   proxy_.Enable(enable);
 }
 
+ModemProxyInterface::Info ModemProxy::GetInfo() {
+  return proxy_.GetInfo();
+}
+
 ModemProxy::Proxy::Proxy(DBus::Connection *connection,
                          const string &path,
                          const string &service)