Adding support to fulltext and ngram index definitions in mappings.xml.

The XCQL2Xpath Stylesheet now interprets constructs like the following:
	<index key="myFulltextIndex" index-type="fulltext"/>
	<index key="myNgramIndex" index-type="ngram"/>

These are translated into:
	myIndexPath[ft:query(.,$term)]
	myIndexPath[ngram:contains(.,$term)]