[VM] Address logic and code restructure

[austinabell]

• Implements Address Type #15 but excludes cbor and json marshalling and unmarshalling because a consistent process should be done in another issue instead of being grouped with this one
• Supresses or fixes linting issues (warnings were really starting to annoy me, sorry I didn't do in another PR)
• Used existing test vectors from go implementations

Basically what the encoding and decoding does is be able to ambiguously decode addresses for the different addressing protocols (ID, Actor, Secp, BLS) and be able to encode them back to a consistent string. Other functionality includes encoding and decoding from bytes and verifying a checksum for a given address. Some random tests can be added for addresses, but I didn't think it was necessary.

[ansermino]

Awesome work!

Generally I feel like this should not "support" an undefined protocol/address. Looking at go-filecoin it seems they mostly return errors for these things, although they do sometimes return the undefined address as well. From a design perspective I think their implementation choice is kind of shitty and should be avoided here.

[austinabell]

The goal was to keep logic and capabilities the same as the other implementations because of the lack of a defined spec on the addressing but thinking about it more it probably would be better to just wrap the address in an Option anytime it is used in other modules to achieve basically the same thing

[GregTheGreek]

New commits LGTM