Updated/stable(afaik): 0.8+ (?) json save / load of npc, player, inventory, and all associated class data. Automagically upgrades current saves.

Rebased to merge clean
 
Also:
* Versioning for mapbuffer and overmaps.
* All backwards compatibility load functions (will be) tucked away in savegame_legacy.cpp
* Consistent syntax between save/load functions of main objects (player/npc/monster/item), which allowed for:
* Json dumper/editor/reloader in editmap (savetest under item menu, 'm' over npc or monster)
 
Todo:
* Remaining iostream hairballs in game.sav, fields and traps. This involves a relatively
  minor amount of work.
* Better documentation.
* Cleanup of deprecated stringstream saves, movement of old streamloaders to savegame_legacy, and
  remaining json loaders to savegame_json.cpp
* Evict weather data to it's own file and have it retain past weather