improvement idea - report handled formats

[rob-metalinkage]

trying to find what formats are handled - and in the context of an extensible module - hers and improvement idea:

provide a means for the handlers to report what formats they support and some way to provide user documentation. If the handlers do this and the module provides the API to expose it to user apps then reusable documentation can be bundled with any third party extensions.

Docs might be scoped to multiple levels:

1. packaging (i.e. requirements for a zip file - such as internal structure assumptions
2. file format - extension, encodings etc
3. fields
4. process
5. outputs (user visible)

intermediate handlers the user doesnt directly interact with might only populate process documentation to record what is being done.