big improvements to tutorial, especially page 2 (matrix arithmetic).

add placeholders for some 'special topic' pages.

doc/examples/tut_arithmetic_scalar_mul_div.cpp

@@ -0,0 +1,17 @@
+#include <iostream>
+#include <Eigen/Dense>
+
+using namespace Eigen;
+
+int main()
+{
+  Matrix2d a;
+  a << 1, 2,
+       3, 4;
+  Vector3d v(1,2,3);
+  std::cout << "a * 2.5 =\n" << a * 2.5 << std::endl;
+  std::cout << "0.1 * v =\n" << 0.1 * v << std::endl;
+  std::cout << "Doing v *= 2;" << std::endl;
+  v *= 2;
+  std::cout << "Now v =\n" << v << std::endl;
+}