* Advantage of KisSharedPtr over boost pointer ?
 * The difference with boost share pointer is that in boost::shared_ptr,
 * the counter is kept inside the smart pointer, meaning that you should
 * never never remove the pointer from its smart pointer object, because if
 * you do that, and somewhere in the code, the pointer is put back in a smart
 * pointer, then you have two counters, and when one reach zero, then the object
 * gets deleted while some other code thinks the pointer is still valid.
 *
 * Inconvenient of KisSharedPtr over boost pointer ?
 * KisSharedPtr requires the class to inherits KisShared.
 *
 * Difference with QSharedDataPointer
 * QSharedDataPointer and KisSharedPtr are very similar, but QSharedDataPointer
 * has an explicit constructor which makes it more painfull to use in some
 * construct. And QSharedDataPointer doesn't offer a weak pointer.