Added items to menu to switch between common and scentific names.

When displaying the news home page the GET parameters are checked
to see whether the names parameter has been specified. If not the
value is taken from either a cookie, so that the user always sees
species name in their preferred form, or from a default setting.
A redirect is performed back to the news view, ensuring that the
names query string parameter is always set. This enables two new
items to be added to the "More" menu to switch between displaying
species using either the common or scientific name.
Empty fields on the search panel are now excluded from query.