moved purely "array" related stuff to a new module Array.

This include:
 - cwise Pow,Sin,Cos,Exp...
 - cwise Greater and other comparison operators
 - .any(), .all() and partial reduction
 - random

test/cwiseop.cpp

@@ -25,6 +25,7 @@
 
 #include "main.h"
 #include <functional>
+#include <Eigen/Array>
 
 using namespace std;