Addd high level introductory docs for all the libs

include/osg/Export

@@ -56,4 +56,12 @@
     #endif
 #endif
 
+/**
+
+\namespace osg
+
+The core osg library provides the basic scene graph classes such as Nodes,
+State and Drawables, and maths and general helper classes.
+*/
+
 #endif

include/osg/UnitTestFramework

@@ -25,10 +25,18 @@
 #include <list>
 #include <fstream>
 
+/**
+
+\namespace osgUtx
+
+The osgUtx is a unit test framework.
+*/
+
 namespace osgUtx{
 
 class TestVisitor;
 
+
 /**
 Test, an abstract base class, is the Composite pattern's \em component
 class for our graph of test cases, and defines the basic interface