Add comment and post doc fields to enable indexing all comments/posts regardless of status.

- For some applications it is useful to index all posts/comments (drafts, spam, trashed, etc)
- post_status and comment_approved fields indicate the status of the doc
- public booleam indicates whether the doc is publicly available (eg should it be shown to front end users vs admin users)
- By default the wpes-lib indexing code still only indexes public docs (all docs in the index are public), these fields just enable custom uses if desired.