Added custom item names support, if an item has an existing custom name when it's turned into a 3D drop, it will be shown instead.

Added "/drops toggle-nametags" command. Requires 'betterdrops.toggle-nametags' permission, true by default.
This is a harmless command that allows players to toggle whether they see nametags of dropped items.
It will immediately take effect for the player that executes the command, players do not have to rejoin.
It does not affect what other players see.
Toggled players will persist after restarts, their UUIDs will be saved to toggled-players.yml.