create savegame.h, add legacy_monster_id to future-proof enum/json shuffling
monster::save/load: save save/load monsters as strings. Tis makes
use of tile_id_data.h on save and on load, which is temporary until
monsters are jsonized.

Everything before this (int mon_id) is translated from int to str
via legacy_monster_id.
Killcounts are json with string ids
Fix reversed NPAGE/PPAGE
Make up/dn/left/right = k/j/h/l, to match rest of game
Make upleft/upright/downright/downleft = y/u/n/b, to match rest of game
New blacksmithing recipe: cooking pot
Tweak.
Long underwear top, slight renaming of vanilla long underwear.
Spawns.
Union suit!
Spawns.
Tights!
Spawns.
Add the Volkswagen Type 2. Sort of.
Add spawn points for the hippie van.
Gives the rattlesnake its rattle!
Rain hood and spawns.
Arm warmers, leg warmers, and the associated spawns.
Recipes.
One more recipe.
Vanilla sleeping bag recipe.