core: global io_service and scheduler

Scheduler and time are imported from ndn-cpp-dev.
Forwarder is using the new scheduler API.
Face system is not transitioned yet.

refs #1290

Change-Id: I5679cb50bbf9890a105f663b038f13951403c2b6
diff --git a/daemon/table/measurements.cpp b/daemon/table/measurements.cpp
index 705d3f1..ed01018 100644
--- a/daemon/table/measurements.cpp
+++ b/daemon/table/measurements.cpp
@@ -13,8 +13,7 @@
 
 const time::Duration Measurements::s_defaultLifetime = time::seconds(4);
 
-Measurements::Measurements(boost::asio::io_service& ioService)
-  : m_scheduler(ioService)
+Measurements::Measurements()
 {
 }
 
@@ -92,9 +91,9 @@
     return;
   }
 
-  m_scheduler.cancelEvent(entry->m_cleanup);
+  scheduler::cancel(entry->m_cleanup);
   entry->m_expiry = expiry;
-  entry->m_cleanup = m_scheduler.scheduleEvent(lifetime,
+  entry->m_cleanup = scheduler::schedule(lifetime,
                          bind(&Measurements::cleanup, this, it));
 }