Fix #881 rounded date to string w/o UTC offset
Previously there was no combination of methods that would generate a rounded AbsoluteDate without UTC offset, which was the behavior of AbsoluteDate.toString() in Orekit 10. Added methods and tests.
Previously there was no combination of methods that would generate a rounded AbsoluteDate without UTC offset, which was the behavior of AbsoluteDate.toString() in Orekit 10. Added methods and tests.