Simplified test case result variable definitions
* variables containing the output of a external function can be defined using the "select" attribute
** tree-like definition is only needed when helper templates such as "transformer" are used
** queries on variables that are instantiated in this fashion need the "self::" prefix before base nodes
* changed includes of the "testcase.xsl" base template to imports
** this signifies that the importing template is based on the imported template
** ... and this is exactly what we want to define