Upthorn - Data saving for persistent game worlds

by Upthorn for Battle for Wesnoth

This is the Persistent Gameworld idea from wesnoth's wiki. If accepted, I would communicate extensively with the community to determine a solution that provides gameworld persistence with the greatest ease of access and implementation for the established community of world and campaign builders for Wesnoth. Currently, I expect that this will involve extending WML, and creation of some system of communication about the extended WML for multiplayer games.