Report errors opening documents during _all_docs

All errors are currently ignored in the receive statements and
eventually we timeout.  This patch causes fabric to report the error and
terminate quickly instead of waiting.

BugzID: 24580
Log errors when doc reads fail for _all_docs

This makes sure that we log any errors while opening a doc during an
_all_docs request. It also passes the failed DbName and DocId to the
user supplied callback function.

BugzId: 24580
Merge pull request #131 from cloudant/24580-receive-errors-on-post

Report errors opening documents during _all_docs

BugzID: 24580