Allow fileglobs in the dont_load list

[ianepperson]

Permits file globbing definitions in the dont_load list by creating a list subclass called PathList which inspects file globs too. When this change is applied, a user can use *, ? and even [seq] to fine tune the dont_load list.

This change uses the Python standard library file globbing (not regex), and thus does not effect existing functionality - the special glob characters (*, ?, [, ]) are not permitted within a Python identifier.

SHELL_PLUS_DONT_LOAD = [
    "my_app.Tagulous_*",  # Don't load any of the Tagulous models defined in my_app
    "*.Tagulous_*",  # Don't load any of the Tagulous models in any app
    "my_app.model[ABC]",  # Don't load modelA, modelB nor modelC
    "my_app.model?",  # Don't load any of the above, plus any other modelD, modelE
]

---

I'm using the Tagulous plugin which creates additional models every time I add a tag field. Each of these models is prefixed with my_app.Tagulous_ and fails to load in shell_plus. I keep adding to the DONT_LOAD list, and I'd rather do that once.

SHELL_PLUS_DONT_LOAD = [
    "my_app.Tagulous_*",
]

[ianepperson]

Can I get a maintainer to approve running the workflows to ensure this works as advertised?

[trbs]

Can you rebase this PR ?