Make domestic herd animals capurable

[leper]

Domestic herd animals like sheep and goats should change ownership to the player that has the most units in visibility range of the animal (other animals shouldn't be counted).

• To achieve this behaviour one should add a RangeQuery to the "ANIMAL" state in UnitAI.js.
• The animal would become property of a player, and have their colour for it's selection ring
• The animal can only be tasked to move by the player who owns it
• The animal can be recaptured by another player.
• Any player (whether they own the animal or not) can stil kill and harvest from it.

Note: #997 specifies some additional enhancements, but those are NOT needed for the completiton of this ticket.