Add more ways to store gas

[Trent VanSlyke]

While Gas Tanks are vertically stackable and can contain large volumes of gas, they are not very useful if there are several types of gas involved. They don't have any special mechanics that could make them interesting, either.

A block capable of storing several types of gas could be added that mimics the mechanics of Tinkers' Construct smelteries while keeping the density mechanics of Gases Framework. Pumps could extract light gases from the top and heavy gases from the bottom. Since gases would be mechanically mixed in this environment, reactions could also occur here.

Alternatively, instead of introducing new blocks for this, the existing gas tanks could be altered for this behaviour.

[Erlend Åmdal]

If gas tanks were upgradable in size as long as the structures are cubic, the merging would be simplified quite a lot. There could also be a high-end gas storage that can store gas like a TC smeltery.