Remove :inherited-members: from most classes, and add :undoc-members:

[mhsmith]

Removed :inherited-members: from all classes, except Widget, which inherits many of its members from Travertino. We could do this one widget at a time as we proceed, but I'd prefer to clean them all up now because it makes the docs much easier to navigate.

Added :undoc-members: to all classes that don't currently have it. All public members should have documentation, so this setting means that if we ever forget to document a member, it will still appear in the documentation, making it more useful to users, and more obvious to us that something is missing.

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[freakboy3742]

👍

All makes sense; I was thinking we'd do this as part of the doc review of each widget, but it doesn't hurt to get a headstart.

I had removed undoc-members on the basis that we shouldn't ever have undocumented members - but I guess you're right that there's no problem having it there as something that should be a no-op, but if we ever forget a docstring, it's at least present in the docs.