Add ESRI's XSLT for ISO 19139 documents

ESRI Geoportal Server's XSLT has been modified:

* Allow standalone rendering
* Support both gmi:MI_Metadata and gmd:MD_Metadata root elements

TODO replace properties with relevant text
Add properties to the ISO XSLT file

Via a quick and dirty script, included in this commit. The properties
have been left defined in the get_property template in case we want to
support i18n in the future.
Don't show link to HTML if document is not ISO