Define tracks and statuses, apply to existing BIPs

I think we should define "informational" vs "standards" tracks similar to this: https://github.com/bitcoin/bips/blob/master/bip-0002.mediawiki#bip-types and then maybe re-evaluate the existing HIPs. I think all the existing HIPs are actually informational because they do not apply do layer-1 blockchain consensus and "implementers are free to ignore them."

We should probably also define statuses like this: https://github.com/bitcoin/bips/blob/master/bip-0002.mediawiki#BIP_status_field and I think all HIPs so far submitted are technically "final" -- and I think at this stage we can probably open PRs with that status.