add forward declaration examples

add classes

CPlusPlus/Classes/Entity.cpp

@@ -0,0 +1,10 @@
+#include "Entity.h"
+using namespace MyNamespace;
+
+Entity::Entity() // constructor definition
+{ }
+
+Entity::Entity(std::string n) : _name(n)
+{
+	//_name = n;
+}