Fixup server replays2

*** Experimental ***

This branch appears to fix server-generated replays at least for "vanilla" 1v1 replays.

Issues: 
- I originally tried to fix this by writing to the history the same way that I write "record_change_controller" to history. It appears that that is not appearing in the replays, although the clients do receive these messages (!). What's going on there? What has to be done for those to show up?
- Shouldn't wesnoth fail more gracefully, i.e. with a "mandatory WML child missing" rather than "assert failure" when missing the [start] tag in replays?
- Is there some way to make the "load game" dialog in multiplayer detect replays and make them load?
- What other kinds of replays are still broken. Presumably reloaded games are, but this at least might get us back to the baseline of 1.10 performance.