Crcengine

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* Feature: Introduction of CrcParams type to parametrize CRC implementation functions.
* Feature: Addition of "window" CRC calculation accepting bit start and end positions
* Bugfix: Fix CRC polynomials under 8 bits wide resulting in an invalid shift and resulting Exception
* Deprecation: passing separate polynomial with and seed is deprecated, passing CrcParams should be used instead.
* Switch to using poetry for packaging instead of setuptools.

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Bug 325 Fix for incorrect result when reflected input bytes are selected with a non-zero
seed.

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Correcting issue relating to module import order for version.py

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* Correcting metadata for python version in setup.cfg

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* Fixed code generation for algorithms whose result doesn't wholly fill a data-type
* Added unit tests for generated C, run using Ceedling_
* Added command-line entry point
* Added support for invoking as a module via python -m
* Switched over to using setup.cfg rather than setup.py
* Python 3.9 support added

.. _Ceedling: https://github.com/ThrowTheSwitch/Ceedling

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Added Sphinx documentation