Add RHIZOME_BUNDLE_STATUS_MANIFEST_TOO_BIG enum option to indicate
that the manifest exceeded 8 KiB in size.
Refactor rhizome_add_manifest() and rhizome_manifest_finalise()
to return 'struct rhizome_bundle_result' instead of 'enum
rhizome_bundle_status', so that that their detailed failure messages
can reach the HTTP API layer instead of just being logged.
Fix HTTP response status codes produced Rhizome direct HTTP requests
to be consistent with the Rhizome RESTful API.
3f8f0f6fc7