v0.0.2: make binarize process PAGE-XML (with AlternativeImage):

First release

• detect whether input file was image/* or PAGE-XML
• for image file, also generate a skeleton PAGE-XML
  (with AlternativeImage for the binarized result)
• for PAGE-XML file, detect namespace (and prefix),
  then check whether AlternativeImage already exists
  or find imageFilename (both on disk and as METS ID),
  process image and add AlternativeImage for result
• reference all new files (image under OCR-D-IMG-BIN,
  PAGE-XML under output fileGrp) in METS
• encapsulate, add pointers for improvement of bashlib
  in core
• improve documentation