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/name-components.h b/model/name-components.h
index 5c06bd9..2cdfd99 100644
--- a/model/name-components.h
+++ b/model/name-components.h
@@ -21,11 +21,11 @@
 #ifndef _NDN_NAME_COMPONENTS_H_
 #define _NDN_NAME_COMPONENTS_H_
 
+#include "ns3/simple-ref-count.h"
+
 #include <string>
 #include <list>
 
-#include <ns3/simple-ref-count.h>
-
 namespace ns3 {
 namespace NDNabstraction {
 namespace Name {