Include conflicts parameter in doc_options

Include conflicts parameter in doc_options

When a keys array is passed to _all_docs, fabric translates this
to individual open_doc calls. The conflicts=true query parameter is
specified as a view-level option and is not, by default, parsed as
an option that should be passed to open_doc.

As a workaround, explicitly copy the view-level conflict parameter into
the document options before open_doc is called.

An alternative approach would be to address this when the query
parameters are parsed, setting conflicts=true in both #mrargs and
detail of fabric, I elected to make the change here instead.

Fixes #COUCHDB-3264