Particle

**First Python 3 (3.6+) only version.**

- `Particle` class:
- Deprecated method `find` method removed. Use `findall` or `finditer` instead.
- HTML Greek letters in particle names use hex code rather than entity name.
- `PDGID` class method and related standalone functions:
- Deprecated function `is_composite_quark_or_lepton` removed. Use `is_excited_quark_or_lepton` instead.
- Documentation:
- README updated with info on the new experiment-specific module `particle.lhcb`.
- Miscellaneous:
- Support for Python 2 and Python 3.5 dropped.
- Full static typing implemented.
- Tests:
- Pre-commit hooks updated.

- `Particle` class:
- New class method `Particle.from_name`.
- New experiment-specific module:
- Module `particle.lhcb` with functions and mappings to deal with particle names in use in LHCb software.
- Script `admin/dump_pdgid_to_lhcb.py` to generate the PDGID <-> LHCb name mapping (CSV file).
- Tests:
- Updated pre-commit hooks.

- `Particle` class:
- Faster `Particle.from_pdgid`.
- Better coverage of documentation for `Particle` methods, especially for newest method `finditer`.
- Do not expose converters on high-level imports. Usage is hence `from particle.converters import ...`.
- Tests:
- Resurrected tests on "all" platforms - Linux, macOS and Windows.
- Performance benchmark tests added for loading of particle property CSV files.
- Updated pre-commit hooks.
- Miscellaneous:
- Enforced `Black` formatting in notebooks.

- Fixed a regression with the import time being unreasonably slow.
- Restore Python 3.5 support (no benefit to drop until 2.7 is dropped)

- `Particle` class:
- Added `finditer`, which returns an iterator instead of a complete list like `findall`.
- Method `find` deprecated. It will be removed from version 0.17.0 onwards.
Please use the more general `findall` method, or the new `finditer` method.
- `PDGID` class:
- New functions `is_sm_lepton`, `is_sm_quark` and `is_excited_quark_or_lepton`
for qualification of PDG IDs.
- `is_composite_quark_or_lepton` deprecated in favour of better named `is_excited_quark_or_lepton`.
- `is_lepton` fixed to match the behaviour of the related `is_quark`,
i.e. now excited leptons are not considered leptons (only SM and 4th generation leptons).
- Improvements to documentation.
- Test suite enhanced accordingly.
- Data files:
- Added the 2021 PDG data table .mcd file, now default.
- Version 10 of package CSV data files:
- Since PDG 2021 information now the default.
- Lifetimes of neutrinos set to infinity.
- Check added for duplicate entries in .mcd PDG data files.
- Tests:
- Tests of coverage added back, using Codecov on GHAs.
- CI enhanced, e.g. adding codespell, isort and flake8 checks tp pre-commit hooks.
- Miscellaneous:
- Support for Python 3.10 added.
- Several `FutureWarning` warnings fixed.
- Code modernisation.

- `Particle` class:
- Bug fix in `Particle.to_dict`.
- Tests:
- CI improvements.
- Azure pipelines removed since superseded by GitHub Actions.
- Miscellaneous:
- Code improvements thanks to Sourcery.
- Clean-up of unnecessary files/code.