Ability to rebind hotbar-loading numbers separately from hotbar slot numbers

[muzikbike]

Same idea as #27, #32 and #33. Currently the keybind used to switch to a hotbar slot is the same key used for deciding what hotbar number to save/load, but it'd be nice if these could be bound separately.

[Minenash]

This is a maybe, while it goes with the theme of "Rebind All The Keys", this doesn't seem too useful, especially with how many keybinds this would add on a screen that doesn't have collapsible sections