Copy_offset and copy_limit shouldn't persist in URL

Added copy_offset and copy_limit to stop_parms definition so that they
don't persist in URL when returning to search results or launching
subject/series searches.

Signed-off-by: Kathy Lussier <klussier@masslnc.org>
Signed-off-by: Pasi Kallinen <pasi.kallinen@pttk.fi>
Signed-off-by: Ben Shum <bshum@biblio.org>