Bug 6594: Schema.org span nesting improvements

So, it turns out that the <a href> was causing a new "chain" to be
invoked, thus nesting the <span> elements for properties within the <a
href> actually caused the properties to be attached to that new chain
rather than the containing object. Therefore, wrap the <span> elements
around the <a href> elements where applicable.

Thanks to Manu Sporny in #rdfa for helping me to sort this out.

Signed-off-by: Dan Scott <dan@coffeecode.net>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
I tested by validating against the Google rich snippet tool,
validator.nu, and linter.structured-data.org. All were satisfied
with the microdata markup, and the properties that are set make
sense.

These patches are only for MARC21 XSLT view, but I think it is worth
pushing them even without the NORMARC and UNIMARC markup, so that
people can start to test out schema.org microdata in Koha, and
refine the implementation.