Inventory Slots

Inventory visibility controls, contributed by BungeeDEV (https://github.com/BungeeDEV, pull request #6).

- Containers only preset: show numbers for chests, furnaces and other containers while your own inventory stays unnumbered
- Separate switches for container slots, your survival inventory, creative inventory, player rows and hotbar beneath containers, HUD hotbar numbers and widget numbers
- Turn numbers on or off for a whole inventory type, including modded menu types
- Exclude a specific menu title, useful for chest-based server menus
- Settings screen organised into Visibility, Appearance, Inventories and Excluded menus tabs, with a live preview
- Keybinds for each visibility option, the current menu title and the current inventory type; they also work inside open inventories (unbound by default, HOME and END unchanged)
- English and German translations
- Config values are validated, saved safely, and a damaged config is backed up to a .bak file

Also includes the earlier fix for slot numbers not showing in the player inventory and crafting table, and the optional widget numbers.

License: MIT.