model: Change default behavior to cache unsolicited data from local applications

In many cases, when a real NDN application is written, it is desirable
to be able to push content to the local cache (e.g., "pre-publish").

http://redmine.named-data.net/projects/ndnsim refs #1002
diff --git a/model/ndn-face.cc b/model/ndn-face.cc
index b3a43b0..625af55 100644
--- a/model/ndn-face.cc
+++ b/model/ndn-face.cc
@@ -76,6 +76,7 @@
   , m_ifup (false)
   , m_id ((uint32_t)-1)
   , m_metric (0)
+  , m_flags (0)
 {
   NS_LOG_FUNCTION (this);
 
@@ -194,6 +195,13 @@
   m_ifup = up;
 }
 
+void
+Face::SetFlags (uint32_t flags)
+{
+  m_flags = flags;
+}
+
+
 bool
 Face::operator== (const Face &face) const
 {