Draft: Add XPath satisfiability test on schema

Satisfiability of XPath queries means that there could be any XML document valid on a given schema which, if the XPath query is run on the document, it will return any result. This could be useful for XSLT and other document transformations/validations.

I will leave a link to some research articles for further understanding:

• Satisfiability of XPath on data trees, Diego Figueira
• Satisfiability-Test, Rewriting and Refinement of Users’ XPath Queries According to XML Schema Definitions

I will rebase the haja.floring/addXPathVerification on master, since I created the branch from win-build, which adds build settings for Visual Studio (BTW, I'm working under Windows and Visual Studio, which offer a nice debugging interface)