Loads a set of xslt rules from the given file for the given result tdom
into a Templates object. Sends error message if parsing error occurs.
The result tdom is identified by the classname of the tdom package.
(There are different Templates objects for different target tdoms, because
the "verbatim element names" of the source text will be interpreted differently.)
callingLocation - may be ==null only for top-most source from command line