Added "overlay" functionality for player/NPCs.

New tileset IDs:
- overlay_worn_{ITEM ID}, overlay drawn over the character when the item is worn
- overlay_wielded_{ITEM ID}, overlay drawn over the character when the item is wielded
Removed superfluous null-check for worn items.
Fix draw_entity_with_overlays return type.

Function doesn't return anything.
Replaced item.type->id with item.typeId() in player::get_overlay_ids()
fixed scrolling in keybinding window
Sushi!

Soy sauce and horseradish are found with other condiments - fastfood,
dining, and kitchen.
Cookbook is found in homebooks and kitchen groups.
Food is craftable-only until we get a sushi restaurant *HINT* where we
can spawn these things in a special item group.
Tweak.
Tweak.
Book spawn tweak.
Fixes missing flag in bigun.
When loading active items, increment the active_item_count.
Servings tweak.
Remove outdated comment.
changed the sheltered survivor profession to wear pants instead of jeans to not start out encumbered
blockhead tileset: add missing entry for 't_concrete'
Blockhead tileset: add missing 'bg' to 't_concrete' and fix whitespace
Swiss Army knife isn't much of a knife...

...so remove it from the weapons list and make it match the (plain, old)
pocket knife instead. Same for the multi-tool.
Fix some warnings found by clang.

Closes #9032.
Canvas bags and sacks, and crafting them.
Commercial fertilizer (solid) coming in canvas sacks as opposed to plastic bags.