Hubmap-api-py-client

- Support queries for and by dataset
- Support queries for all entities by identifier
- Examples of query by cluster
- Example of query for cell by protein
- Reworking client-side parameter validation
- Integrating hubmap_cell_id_gen_py into examples
- Supporting queries for all entities of a particular type, including proteins
- Expanding table in readme
- Fewer preflight checks on requests: These are a maintenance burden.

- Remove complement magic method, and add difference.
- Require "has" param to be list, and update examples.
- Add subtypes of ResultsSet, and check that operands on set operations match.
- Issue templates
- Rename repo and package.
- Move to github CI
- Add ASCT-B to matrix in README
- Improve input validation logic
- Use slice syntax to get list

- Change to more fluent SDK: `select_TARGET(where='SOURCE', has='CRITERIA', ...)`

- OO interface: Fewer details need to be repeated across methods, because they are kept in the object.

- Basic python interface: methods mirror API hits.