Made extensive use of XSLT to define new tag in application XML files, <def>,...

Made extensive use of XSLT to define new tag in application XML files, <def>, which allows documenters to link, with minimal effort, to a definition from the ISIS Glossary.  Furthermore, the Glossary XML page has been made more user-friendly with XSLT so that now all one needs to do is add a new definition with the <definition> tag, and a translation file takes care of all the formatting.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@3331 41f8697f-d340-4b68-9986-7bafba869bb8