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Using Cloud Storage could generate urls like:

`https://storage.googleapis.com/<BUCKET_NAME>/<PATH>/testwebm?Expires=1612931745&GoogleAccessId=<ACCOUNT>&Signature=<SIGNATURE>`

Passing parameters to the URL returns None in mime.guess_type(url)

Also, extracting the mimetype to some property that can be reused. Similar to https://github.com/wagtail/wagtail/blob/master/wagtail/documents/models.py#L170

Conditionally show some things only if modeladmin is installed, addded links for editing/adding tracks

This reverts commit 2613094d.

Change to use packaging.version to compare version numbers (because string comparison means 2.10 > 2.7 is not True)