Various documentation updates:

- update the tutorial
- update doc of deprecated cwise function
- update cwise doc snippets

doc/snippets/Cwise_product.cpp

@@ -1,4 +1,4 @@
-Matrix3i a = Matrix3i::Random(), b = Matrix3i::Random();
-Matrix3i c = a.cwise() * b;
+Array33i a = Array33i::Random(), b = Array33i::Random();
+Array33i c = a * b;
 cout << "a:\n" << a << "\nb:\n" << b << "\nc:\n" << c << endl;