Removed gtest based test cases and added program options
* selectively testing document construction in plain C++ code has turned out to be more work than worth it
** i.e. removed test cases and GTest dependency
* added boost::program_options based frontent to InputXSLT
** example command: "./test --transformation ../dummy/transform.xsl --target out.xml"
** the plan is to use a simple shell script that generated test transformations and compares the output to reference files