MCR-3092 XSL test capabilities

[michael-becker]

Link to jira.

MCRTestCase contains new methods

• parse: parses a given XML structure using a given XSL file
• xmlTest: encapsulates an XML structure in an XML document for test

Usage:

• create a test.xsl file containing match templates calling functions/templates to test (e.g. classificationTest.xsl)
• parse a structure/empty XML using the parse-method in MCRTestCase
• call Junit-assert-statements using the resulting XML structure

see usage example in XSLClassificationTest