Huge engine change, replace all std::shared_ptrs

Create a new shared pointer type stdext::shared_object_ptr and stdext::shared_obj
using boost::intrusive_ptr

Advantages:
 * half memory usage
 * faster and lightweight

Disadvantages:
 * using weak_ptr is not supported anymore
 * compiling seems slower

src/framework/graphics/image.h

@@ -26,7 +26,7 @@
 #include "declarations.h"
 #include <framework/util/databuffer.h>
 
-class Image
+class Image : public stdext::shared_object
 {
 public:
     Image(const Size& size, int bpp = 4, uint8 *pixels = nullptr);