Allow Proxy to take more than 1 variable cards

[changhe3]

Issue type:

• :heavy_plus_sign: Feature request

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Short description:

Currently it's quite cumbersome to make a relatively long list from a bunch of variable cards. Say you have 8x8 botania flowers and you want to read their Tile Entity NBT for some automation, and you would need to do 64 appends to make a list out of it. I think Proxy should have a much larger internal inventory like Variable Store, so that you can just put all those variable cards into it and get a reference to the list.

Same as #192

[rubensworks]

Thanks for the suggestion!