Add namespace information to <modsCollection>

Got the namespace info from a sample MODS file that Eric got from Melanie.
However, I changed xmlns:mods="http://www.loc.gov/mods/v3" to
xmlns="http://www.loc.gov/mods/v3", thus making it the default
namespace. Also, I included other name space declarations, xsi and
xlink. xsi seems to be used for the schema declaration. Not sure about
xlink
Fix bugs

This includes also changing the way tge <modsCollection> element is generated, in order
to be able to add the namespace attributes and schema without xslt doing weird stuff
(adding the name space in the <modsCollection> affects the namespaces used
by xslt while processing - or something along those lines. So had to output the
<modsCollection> element and attributes via <xsl:text> instead of just including in
the xslt xml.