more documentation and examples, add Doxyfile and Mainpage.dox and also

the benchmark program

doc/examples/function_dynBlock.cpp

@@ -0,0 +1,19 @@
+#include "../src/Core.h"
+USING_EIGEN_DATA_TYPES
+using namespace std;
+int main(int, char**)
+{
+    Matrix4d m = Matrix4d::identity();
+    m.dynBlock(2,0,2,2) = m.dynBlock(0,0,2,2);
+    cout << m << endl;
+    return 0;
+}
+
+/* Output:
+
+1 0 0 0
+0 1 0 0
+1 0 1 0
+0 1 0 1
+
+*/