Replaced custom build system with BuildXSLT
* the bootstrapping transformation is not specific to this project and may be used as a starting point for all kinds of projects making use of InputXSLT
** this is why it was extracted into the separate BuildXSLT repository
* the new "make.xml" _Makefile_ has to be passed as input to "build.xsl"
** e.g. "ixslt --input make.xml --transformation ../BuildXSLT/build.xsl"
* "make.xml" defines the basic transformation chain and its input