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Remove outdated comment.
blockhead tileset: add missing entry for 't_concrete'
Blockhead tileset: add missing 'bg' to 't_concrete' and fix whitespace
Canvas bags and sacks, and crafting them.
Commercial fertilizer (solid) coming in canvas sacks as opposed to plastic bags.
Italian seasoning, black pepper, and seasoned salt coming in canvas bags.
SAI posts and fungicide in plastic bags
Merge pull request #9042 from Rivet-the-Zombie/sushi

Sushi!