[RPD-298] Create stack add command

[Christopher-Norman]

This PR adds a stub command for adding a module to the stack and a CLI command to call this. Full implementation with a function in core.py will be completed in another ticket.

This PR also includes the changes introduced in the latest bug fix for Matcha (these can be ignored) as the feature branch is out of date.

Checklist

Please ensure you have done the following:

• [x] I have read the CONTRIBUTING guide.
• [x] I have updated the documentation if required.
• [ ] I have added tests which cover my changes.

Type of change

Tick all those that apply:

• [ ] Bug Fix (non-breaking change, fixing an issue)
• [x] New feature (non-breaking change to add functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Other (add details above)