Refactor skill chat card handling to pass Actor and other documents by ID/UUID

[BadIdeasBureau]

Currently, the chat cards pass the data on the originating actor and target by copying the data into the chat card. This potentially leads to issues where one of those actors is subsequently updated, and results in a lot of unnecessary data in the chat database.

Passing by ID (or more likely UUID) would allow an up to date copy of the data to be retrieved when needed - and as a bonus, would likely solve #193 in the process (as that is probably the result of the current method of data storage inadvertently skipping the deprecation path for changes in V10).

This should be doable synchronously (i.e. using fromUuidSync in v10), since I can't see that we would need a Document from a compendium for any of this.