Dantro

- !149 updates dantro's requirements lists and extends the CI to also test for lower bounds of version requirements.

- As of this release, dantro is licensed under the [LGPLv3+ license](COPYING.md), added in !133.
- !141 adds automatic deployment of dantro to the [PyPI](https://pypi.org/project/dantro/).
- !134 adds a [Contribution Guide](CONTRIBUTING.md) and a [Code of Conduct](CODE_OF_CONDUCT.md).
- Furthermore, the dantro documentation is now deployed to Read the Docs, both for [stable versions](https://dantro.readthedocs.io/en/stable/) and for the [latest version](https://dantro.readthedocs.io/en/latest/).
See !140 and !143 for more information.
- 92 adds a test job for a Python 3.8 environment to the CI pipeline
- 132 updates the graph-related vocabulary to `graph`, `nodes`, and `edges`.
- Various documentation improvements
- 124 and !136 fix all broken references in the documentation and the docstrings and improve the Sphinx configuration.
- !135 adds usage examples and includes code snippets from tests, thus automatically making sure that they work as intended.
- Additionally, the CI now exits with a warning if Sphinx emitted any warnings, and a log file is made available via the job artifacts to inspect the Sphinx error log.
- 117 improves, restructures, and extents the documentation, now covering the full range of dantro applications.
- 135 eliminates typos and grammar issues in the documentation making it consistently use American English.


Important notes on upgrading
- Due to the changes introduced in !92, the netcdf4 package is no longer a dependency required by dantro.
It is replaced by the more commonly used scipy package.
To ensure that no interference occurs between a remaining installation of netcdf4 and the new dependencies, we suggest to uninstall it using `pip uninstall netcdf4`.
- With 132, the former `NetworkGroup` (now `GraphGroup`) and some of its attributes are renamed.

- 127 allows to disable `DataManager.load` operations via keyword argument; this is useful e.g. when passing arguments via recursively updated configuration hierarchies.

- 126 makes it possible to overwrite existing plots

- !124 adds a condensed data tree representation (as proposed in 112)
- Minor changes:
- !127 adds a `.coveragerc` file to control pytest-cov behaviour
- !126 changes the type of axis-specific configurations for the `PlotHelper` from list to dictionary
- 101 _removes_ the plot creator auto-detection via plot function signature (deprecated in 0.10, see 100).
- !128 adds the functionality to load plain text files into `StringContainer`
- !130 adds the `PlotHelper.attach_figure` method which allows assigning a custom figure.

- 108 adds the ability to unpack DAG results directly into the plot function invocation instead of passing them as the `data` keyword argument.
- 109 extends the operations database to allow importing callables or objects on-the-fly and use them in DAG transformations.
- Adds the `import` operation which allows importing a module or callable (or any other object) directly, alleviating the need to register a new operation.
- Adds the `call` operation to call a callable.
- Adds the `import_and_call` operation, combining the two.