Added Block Operations tutorial and code examples

doc/examples/Tutorial_BlockOperations_colrow.cpp

@@ -0,0 +1,15 @@
+#include <Eigen/Dense>
+#include <iostream>
+using namespace Eigen;
+
+int main()
+{
+  MatrixXf m(3,3);
+  
+  m << 1,2,3,
+       4,5,6,
+       7,8,9;
+     
+  std::cout << "2nd Row: "
+    << m.row(1) << std::endl;
+}