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* Create `ComparableGroup` class for unordered `Factor` collections
* Create `FactorSequence` class for ordered `Factor` collections
* Eliminate Analogy class, moving its methods to `FactorGroup` and `FactorSequence`
* Add `Factor.consistent_with` method to search for available context avoiding contradiction
* Add "or" operator for `FactorGroup`
* Integrate Legislice API client for retrieving text from US Constitution and US Code
* Remove functions for loading legislation text from XML files. Use API client instead.
* Delete classes for accessing XML legislation files: `Code`, `Regime`, and `Jurisdiction`