Make doxygen modules list slightly more alphabetical

doc/modules

@@ -52,6 +52,6 @@
  *    - a UDP and a TCP implementation
  *    
  * @defgroup applications Applications
- *
- * @defgroup mobility Mobility
+ *    
+ * @defgroup netanim Animation
  */

src/mobility/model/mobility.h

@@ -1,3 +1,7 @@
+/**
+ * @defgroup mobility Mobility
+ */
+
 /**
  * \addtogroup mobility Mobility
  *

src/netanim/model/animation-interface.h

@@ -32,11 +32,6 @@
 
 namespace ns3 {
 
-/**
- * \defgroup netanim Animation
- *
- */
-
 class NetModel;
 
 /**