Add tests that check our argument parsing logic (and fix bug)

See merge request !113

- going the arguments provided by the user
- to the relevant function being called.

Added tests because I discovered a bug that the tests would have caught.

Add example for `get_available_releases`

See merge request !111

return available (i.e. released!) release versions

See merge request !110

from available package sets

More code, but less thinking to understand what it does.

i.e. if mpsd_release == None

It's not perfect that this needs manual updating. On the other hand, this
provides control over what versions are (trivially) visible to users.

Use mpsd microarch consistently

Closes #33

See merge request !108

Remove conditional dependence on rich

See merge request !106

Simplify log file path generation

Closes #24

See merge request !96

Use `logging.error` for error message

See merge request !105

Improve error if current directory (or parents) are not MPSD software instance

See merge request !104

Update log function names and docs

See merge request !107

As this is a python package, we now do rely on rich.

Explain why we think a release has not been fully installed

See merge request !103

Fix double plog output, version 2

See merge request !102

due to color

Remove printing of current working directory to debug message: usually the user
will know in which directory they are, so this information detracts from the
interesting content of the error message.

- as screen width may vary, it is best not to break sentences with \n I think.