The Framework is responsible for providing MetaData regarding any extensions and context for the extension.

Extensions would most likely require some minimal declaration. Such as name of the Class,Assembly (Class,Package).

There are no requirements for the storage mechanism for the MetaData.
Keeping configuration in one place would be recommended but not required.
A tool for editing would also be recommended. This does away with error typing or mistakes that comes from manual editing. Also the maturity of a Framework can be ascertained by its tools (or lack thereof).

Convention over Configuration

To offer good ease of use, automatic value and easier uptake of a Framework, I believe there should always be "convention over configuration". This is often lacking in the horizontal frameworks, or infrastructure frameworks, but really necessary to aid in flattening a Framework's learning curve.