Set up for v4

Set up for v4
Add two new methods which align with Nano node RPC actions. Return more data from hash result. Indicate a more specific `threshold` by passing a full 16-character string to the new `work_` methods. Changed `NanoPowGl.size` property to return total pixel count. Add typings for request and response objects consumed by new `work_` methods. Add more tests for receive threshold edge cases. Improve build process. Expand documentation.