Document local data storage in a spec document

[whyrusleeping]

Description

We need to document what data a filecoin node stores locally. The exact implementation details are not important here, It doesnt matter if you use leveldb or badger or postgres. The main thing I want here is effectively an interface description of the 'Repo', and an indication of what storage operations we have. For example, we have the keystore which we use to track private keys, we have block storage for content addressed data, we have a way to store various bits of chain state, and a pretty solid amount of other stuff.

Acceptance criteria

• More detail than 'filecoin needs a KV store'
• Less detail than every byte that goes where on disk
• Must accurately account for everything we are persisting to disk, and why

Risks + pitfalls

Where to begin

Create a new doc in the specs repo called either repo.md or local-storage.md

[mishmosh]

because it's not protocol-affecting, more of an "implementation suggestions" section, not picking this up at this time