Improvements to publish_lookup chapter

Signed-off-by: David Solt <[email protected]>

- Add PMIX_DATA_TO_PUBLISH directive
- Clarify how an implementation distinguished between attributes and data
- require that ranges for publish and lookup match
- Determine how custom ranges are handled:
    Publisher need not be a member of a custom range
- simplified retrieval rules
- Add PMIX_ACCESS_USERIDS and GRPIDS to list of attributes related to publish
- move callback presentation to Chap_API_Struct chapter
- move lookup structure prior to its use in the chapter

Author: dsolt