#555: oic_validation module improvements
#555: Add docs for oic_validation module
#555: Mention ticket number in TODO
#555:  Expand oic_validation docs
#555: Add deps so RtD can build the oic_validation docs
#555: change "TODO" to ".. todo::" so it shows up in RtD
#555: Add cert verification "todo" to docstring
#555: ".. todo::" doesn't work here, switching back to "TODO"
#555: Merge from origin/qa-develop