Decaylanguage

* Dependencies and Python version support:
- Package dependent on ``Particle`` version 0.13.
- Support for Python 3.9 added.

* Dependencies:
- Package dependent on ``Particle`` version 0.12.

* Dependencies:
- Package dependent on ``Particle`` version 0.11.
- Dependencies on `lark-parser` and others upgraded.

* Dependencies:
- Package dependency on ``pydot`` made a requirement.

* Parsing of decay files (aka .dec files):
- Simplifications in various methods of class ``DecFileParser``.
- A couple more tests added.
* Minor fixes.

* Parsing of decay files (aka .dec files):
- Master Belle II DECAY.DEC file added to the package.
- Certain ``DecFileParser`` class methods made more versatile.
- ``Lark`` parsing grammar file improved.
* Universal representation of decay chains:
- Classes ``DecayChain``, ``DecayMode``, ``DaughtersDict`` and ``DecayChainViewer`` enhanced.
* Dependencies and Python version support:
- Package dependent on ``Particle`` versions 0.9.
- Support for Python 3.8 added.