Schematron / Add multilingual using diagnostics and report successful assertions

Regarding schematron, it could be relevant to introduce some changes if that sounds good to you.

The proposed changes:
* multilingual schematron (using xml:lang attribute and sch:diagnostics)
* report success (and not only failure) using sch:report
* report details of what is tested using variables (set by sch:let and displayed with sch:value-of)
* add XML file for unit testing the schematron rules

Also fix namespaces (pointing to the 2013-06-24 version).

Testing could be done in oxygenxml:

![image](https://cloud.githubusercontent.com/assets/1701393/5568325/f3ffbf8e-8f57-11e4-8080-cd077be11cba.png)


Therefore and before proceeding all schematron files, I would like to check with you:
* if you've any workflow to produce the schematron files (from the XSD tools used ?) or if we can update them directly ?
* if we have to follow any rules for reporting message (use same text as in the standards if available - it will not in the French version of the document) ? or do we have some freedom on this ?
* and if true, could we make the reporting message more "user-friendly" by reporting details (eg. https://github.com/fxprunayre/XML/compare/improvements/schematron/multilingual-using-diagnostics?expand=1#diff-4457ae9573f3864483f93533a8acca6cR70) ?
* for empty text, should we considered the nilReason attribute (eg. https://github.com/fxprunayre/XML/compare/improvements/schematron/multilingual-using-diagnostics?expand=1#diff-4457ae9573f3864483f93533a8acca6cR107) ?


Let me know what you think of thoses changes.