Changed formula so sleep recovery increases over 2 hours to 2x, and removed
fatigue while sleeping and attempting to sleep. 7.25 hours continuous rest
required for a full 16 hour day, giving some leeway for activities that
might increase fatigue, and extended recovery is slightly faster.
Completely replace the oter_id enum by new overmap_terrains.json.
Merge branch 'master' into Crafting
Improve liquid craft container handling WIP
Fixed natural healing.
Merge branch 'master' into buildings_json
Fix overmap terrain allow_road checks.
Style and comment overmap::make_hiway().
Improve container handling WIP
overmap: fix legacy save/load
load_overmap_terrain; pre-set is_river, is_road, and set "id_base" prior to _north, _sw, etc
oter_id: switch from std::string to struct { int _value; } with flexible translation methods
generate: optimize the frack out of it; temporary until over/under etc is jsonized
Merge branch 'master' into Crafting
Turn metal tank into a container.

Also changed volume to reflect holding capacity.
Store fuel on metal tank when removing from vehicle.

Fuel will be stored in a metal tank when it is removed from a vehicle.
Two things to note about this:
    * It will store as much as it can in the tank instead of figuring
      out how much it was holding before
    * The metal will be put on the players inventory so to be able to
      get a reference to it.

These two issues should be worked on in the future.
Use the actual fuel amount in the tank for the refill.

Removing tanks will now remember the amount amount of fuel in them now instead
of being completely filled.
Spawn metal tank on the ground after removal.
Clean overmap::generate_sub a little.
Clean editmap.cpp a little.
Clean overmap::save() a little.
cleanup
Improve liquid craft container handling WIP