Changes in master branch to be aware of

[Griatch Art]

As part of fixing https://github.com/evennia/evennia/issues/2287 I had to do certain changes to the `master` branch as well as `develop` branch, since this issue deals with documentation-building across multiple branches.

The main change has to do with allowing the `evennia` library to run through the documentation building process without requiring a game dir initialized. This could potentially come with other positive side effects for develop work.

The main backwards-breaking thing that people may run into is that the `evennia` top-level library no longer has any of the `BASE_*TYPECLASS` properties defined on them. These were the main reason for causing circular import errors.

These should usually not be that useful since they link back to your normal gamedir/typeclass/ classes, so you can just refer to them directly. But if you did use e.g. `evennia.BASE_ACCOUNT_TYPECLASS` in your code you should be aware that this will now raise an AttributeError.

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Griatch