Added Block Operations tutorial and code examples

doc/examples/Tutorial_BlockOperations_vector.cpp

@@ -0,0 +1,24 @@
+#include <Eigen/Dense>
+#include <iostream>
+
+using namespace std;
+using namespace Eigen;
+
+int main()
+{
+  VectorXf v(6);
+  
+  v << 1, 2, 3, 4, 5, 6;
+
+  //print first three elements
+  cout << "-- head(3) --" << endl
+    << v.head(3) << endl << endl;
+  
+  //print last three elements
+  cout << "-- tail(3) --" << endl
+    << v.tail(3) << endl << endl;
+    
+  //print between 2nd and 5th elem. inclusive
+  cout << "-- segment(1,4) --" << endl
+    << v.segment(1,4) << endl;
+}