* this function essentially provides the same functionality as FunctionTransform with the addition of directly committing the result to the filesystem
** this is needed if one wants to generate doctype-containing transformations from inside a transformation as "write-file" is not able to infer the doctype of a given xalan::XalanNode pointer
** this is a integral limitation of (at least) XSLT 1.0 as implemented in Apache Xalan
*** a document can of course only have a single document type
*** e.g. we can not include a doctype node in the result tree of FunctionTransform
* implemented test case for FunctionGenerate
* transformation "test.xsl" is shared between the FunctionTransform and FunctionGenerate test cases
* modified README.md accordingly

* the external "transform" function now expects a input document as its first parameter
** this input parameter is resolved and passed as input to the transformation
** changed and expanded test case accordingly
* because of xalan internal problem this currently only supports input DOMs loaded directly from the fs
** passing result trees or node sets analog to how the transformation may be passed into the function leads to parsing and assert failures
** parsing node-based input DOMs using xalanc::XalanTransformer::parseSource produces errors concerning base entity resolution
** if the error capacitor instance is temporarily disabled it works correctly as long as one doesn't try to access the input document
*** this causes a assert failure in the XPath implementation (seems to be related to XALANC-540)

* FunctionReadFile is now able to distinguish between XML files and plain text files
** it selects the appropriate course of action automatically
** reading the file as XML into the DOM or reading it as a string
* the current selection criteria is the file extension
** I am thinking about trying to import every file into the DOM and using the result state of that action as selection criteria
* Updated README.md and test cases accordingly

* test case base template contains the basic test case markup
** it was mostly created to include include-path resolution into the test cases
* improved transformer helper template by separating the external function call into its own variable

* the directories below "./test" contain test cases
** "transformation.xsl" and the expected result as "reference.xml"
** tests are performed by "check.sh"
*** returns diff on error
* this system enables simple verification of external function results
** way simpler than C++ unit tests would be in this scenario
* expanded cmake instructions to automatically execute the test cases
* old example transformation was removed