Core/Player: Implement a generic method to send out item retrieval mails...

... as it seems to be used in multiple places and also send disenchant roll result as a mail if the player's inventory is full

Now, now, now... I'm not entirely sure about this... but since as said that it might be used in multiple places, maybe it'd be better. It also allows it's free usage around the core and an easy update when/if we start supporting mail templates read from database.

I've used it to deal with the disenchant roll result when the player's inventory is full as well as by @Aokromes comment.