Update manifest template
Update licensing blurb
Use different version_info style
Update for more modern style

Use more PEP8 style, and use decorators e.g. @classmethod instead of
the older style `foo = classmethod(foo)`.

Also replace the Association.getExpiresIn() method with a property
`expiresIn` (which was already there, weirdly) and replace all calls
to it with uses of the property.
Indentation & cleanup