Partialwrap

* Rewrote Quickstart and User Guide.
* Use formatted strings where appropriate in std_io.
* Removed exe_wrapper_v34 and hence support for < Python 3.7.
* Use dict.get() function for keywords in wrappers.
* Improved docstrings.
* Use sphinx_book_theme.
* Move documentation from ReadTheDocs to Github Pages.
* README and documentation from Markdown to reStructuredText.

* Added error function in `exe_wrapper` as fallback option in case
subprocess exits with error code > 0.
* Added examples and reformatted docstrings.

* Use subprocess.run for Python > v3.6.
* Added `partialwrap` to conda-forge.
* Changed Markdown to reStructuredText in all files but README.md

* Allow empty right-hand sides in files, such as `name1 =`.
* Use helper function for constructing dict for `_msub` in
`sub_params_names_ignorecase` and `sub_params_names_case`.

v1.4.x (Oct 2021)
* Corrected error in docs still using directory structure without src.
* Updated Zenodo, `MANIFEST.in`, and documentation.
* Removed stray print statement.

* Move to new pip structure using `pyproject.toml`.
* Move to Github actions.
* Remove History sections from docstrings of wrappers and IO routines.

* Escape backslash also in params in sub_params_ja routines.