Add creation and resolution of DIDs using method 1

[andrewwhitehead]

Currently in draft until I can do some more testing. The method-1 test vectors are from aries-framework-javascript, and do not pass strict validation in pydid (but invalid documents are still allowed).

• Adds peer DID creation from a genesis document (method 1)
• Adds resolution of a peer DID using method 1: note this requires passing in a received DID document for verification
• Adds a resolve_peer_did_basis method returning a ResolvedBasis instance, making it easier to pull out the relevant keys
• Adds a split_peer_did method which can be used to check the inception method before attempting resolution
• Adds a missing BaseKey.to_base58 method as well as BaseKey.from_verification_method

@dbluhm @swcurran

[swcurran]

@andrewwhitehead — should this be closed, or moved forward? If it is valuable, can it be taken over by someone else — merged onto a branch and evolved?