Custom Model Data or NBT support with Item economy

[Folas1337]

Describe Feature
I'm using items with a certain custom model data which represent a physical form of a currency. My idea to support that is to add the following line to the config.yml:

economy: Item
item economy item: GOLD_INGOT
+ item economy custom model data: 10

By default it could be item custom model data: null which would make the plugin behave as it currently does with an item economy.

As an alternative you could also allow any kind of NBT but I'll make that decision up to you.
In that case I would envision a config.yml like this:

economy: Item
item economy item: GOLD_INGOT
+ item economy nbt: [custom_model_data={floats:[1001]}]

The first suggestion is more catered towards my needs, the latter one would allow for a broader audience.