Use rqid instead of skillOrigin + skillId on weapon item

[wake42]

Breaking Refactoring

The currently used two fields skillOrigin & skillId on weapon / usage can be expressed with just one rqid. When the weapon item is embedded in an RqgActor the RqgActor.getEmbeddedItemsByRqid can be used to find the skill that should be used. And if there is no skill a global search for the same rqid could be used to find the skill to embed on the actor (when dragging the weapon to the actor).

Background

The current skillOrigin uses uuid to find the applicable skill, but the uuid can change if the item has been part of a compendium for example. By using rqid this problem is avoided. It will also make the rqid required on the skill to be able to use the skill on a weapon.