Add method to add multiblocks to a stage

[justinrusso]

Mutltiblocks are staged using a string. There are different methods used for staging the mutliblocks depending on support/etc.

See:

• https://github.com/DarkPacks/SevTech-Ages/blob/master/src/scripts/staging/multiblock/immersive_engineering.zs

• https://github.com/DarkPacks/SevTech-Ages/blob/master/src/scripts/staging/multiblock/modular_machinery.zs