Release pyeit-1.2.0 (API cleanup, which is NOT backward compatible)

Warning: Since version 1.2.0, the API for forward and EIT imaging are NOT backward compatible. You may need to adapt the PyEITMesh and the PyEITProtocol dataset class for your code (which is more cleaner, and requires little coding effort). Please see the example folders for more detail.

What's Changed

• fix diff_pairs_mask to fit original conditions by @DavidMetzIMT in https://github.com/liubenyuan/pyEIT/pull/42
• Issue setup by @DavidMetzIMT in https://github.com/liubenyuan/pyEIT/pull/43
• Issue setup small fix + optional meas_pattern by @DavidMetzIMT in https://github.com/liubenyuan/pyEIT/pull/45
• Add PyEITMesh, PyEITProtocol, PyEITAnomaly by @DavidMetzIMT in https://github.com/liubenyuan/pyEIT/pull/47

Full Changelog: liubenyuan/pyEIT@v1.1.9...v1.2.0