* A christmas tree with presents is now a subtype
Admins can now spawn `/obj/structure/flora/tree/pine/xmas/presents`
directly, instead of spawning regular christmas trees and then
triggering the event.
Also, the event now just deletes and replaces the xmas tree with a
present tree; saves on duplication of icon states and vars and all that.
* Code review I
* Gaia's Landing: The PR
dc6b4e2b61