some fixes to Check:

* fix erroneous specifier to time.Parse
* shadowing of variable caused a check always to fail
* miss-placed continue within a for didn't escaped to outer, bigger for loop
new test file

This one contains no errors or warnings (in required and optional fields)
ogdatjson-checker improvements

* Checker-program emits messages in German; make consistent
* No command-line flags is an error; report
* If there is no error/warning in the meta-data, say so.