BEP Idea: Add support for IPLD

This was an idea that was originally proposed by @TimDaub in the issue bigchaindb/bigchaindb#485

I created this issue so we don't forget about that idea. For all the comments on that issue, see the issue itself: bigchaindb/bigchaindb#485

Start by reading the referenced issue bigchaindb/bigchaindb#485 and its discussion, since this issue contains no implementation entry point or detailed requirements. Before work can be considered done, the project would need an agreed definition of what IPLD support entails; the current issue does not provide completion criteria.

Written by the indexing model from the issue text.