Making epubcheck-adapter work with Saxon 9.5

 * copied and fixed implementations for the functions `saxon:column-number`,  `saxon:line-number` and  `saxon:system-id` from epubcheck to epubcheck-adapter.
 * exposed functions through OSGi

This does not work currently, so don't merge. I'll create another PR for updating the pipeline-assembly dependencies once this is working.

@rdeltour is this the right approach? I'm getting the same saxon error after having added patched implementations of the saxon fuctions. Are epubcheck not seing them for some reason?