Statick-planning

Added

- Add testing support for Python 3.10.
- Add weekly scheduled test actions to identify issues on a consistent basis.
This will catch bugs related to updated dependencies when the code is not modified.

Fixed

- Fixed a bug in the stock planning configuration file.
The name of the tool plugin in the configuration file was not updated to reflect the renamed plugin.
- Fixed pylint warnings related to using the open call without specifying an encoding.

Removed

- No longer supporting Ubuntu 16.04.
- No longer supporting Python 3.5.

Added

- Use new Statick feature of walking directory structure once per package for discovery phase.

Changed

- Convert use of print() and show tool output flags to the built-in Python logging module.
- Rename `val` tool plugin to `val_validate`.
This matches the actual utility name, and provides room to add other utilities from the VAL project.

Added

- Discovery plugin to find PDDL files.
The files are sorted into domain and problem file types based on the contents of the file.
- Tool plugin for the `Validate` application from
[VAL](https://github.com/KCL-Planning/VAL/tree/master/applications#validate).
`Validate` is a utility to check the syntax of PDDL files.
In order to use the tool a domain file is required to have been discovered, and a problem file is optional.