face: Refactor internal PIT to use scheduled events

The commit also changes how face is paused when there are no pending
interests left and there are no registered prefixes with local
forwarder: data structures for pending interests and registered prefixes
will fire up a signal when they become empty.

Change-Id: I6b87a44b0c8bc766865a51962ecacaec85b4adad
Refs: #1372, #2518
diff --git a/src/transport/stream-transport.hpp b/src/transport/stream-transport.hpp
index 737842c..d7f2e49 100644
--- a/src/transport/stream-transport.hpp
+++ b/src/transport/stream-transport.hpp
@@ -127,6 +127,9 @@
       }
   }
 
+  /**
+   * @warning Must not be called directly or indirectly from within handleAsyncReceive invocation
+   */
   void
   resume()
   {