Add a hidden input:submit field in facets form (closes #1988784)
<Enter> is supposed to submit the form only if there is a single
input:text field. However most browsers will submit the form
on <Enter> anyway if there is an input:submit field.
see: http://www.w3.org/MarkUp/html-spec/html-spec_8.html#SEC8.2
Firefox 7.0.1 does not submit form on <Enter> if there is more than a
input:text field and not input:submit but does it if there is an
input:submit.
IE 6 or Firefox 2 behave the same way.
doc/book usr/share/doc/cubicweb-documentation
doc/html usr/share/doc/cubicweb-documentation
debian/cubicweb-doc usr/share/doc-base/cubicweb-doc