Moving apps back to apps/ folder. Finally worked out the problem with headers
WAF building system copies all headers to one directory. As a result,
all #include directives in all NS3 modules should be either in form
"ns3/header-file.h" or just "header-file.h", disregarding the actual
directory structure.
diff --git a/model/content-object-header.h b/model/content-object-header.h
index 454f8e2..ff2ae26 100644
--- a/model/content-object-header.h
+++ b/model/content-object-header.h
@@ -22,8 +22,8 @@
#ifndef _CONTENT_OBJECT_HEADER_H_
#define _CONTENT_OBJECT_HEADER_H_
-#include <ns3/integer.h>
-#include <ns3/header.h>
+#include "ns3/integer.h"
+#include "ns3/header.h"
#include <string>
#include <vector>