Support for non-vanilla inventories

[the-vindex]

This is more of a feature request - essentially if I put the table near non-vanilla (double)chest, I would like to see contents of that inventory. If it's size does not exceed double chest, you won't even have a problem with rendering. Of course support for all sizes of chests would be appreciated.

Another question is - what should happen if you put a barrel near werkbench (if support above is added).

[jakimfett]

I'm probably going to wait a bit before I start tackling non-vanilla storage types. Eventually I'd like to have at least Iron Chests support. I don't know about barrels, but it's definitely something to think about!