ADD: new track message, Entity class and Position class

libs/eigen/doc/examples/Cwise_lgamma.cpp

@@ -0,0 +1,9 @@
+#include <Eigen/Core>
+#include <unsupported/Eigen/SpecialFunctions>
+#include <iostream>
+using namespace Eigen;
+int main()
+{
+  Array4d v(0.5,10,0,-1);
+  std::cout << v.lgamma() << std::endl;
+}