Correct validation for required fields in variadic groups (#314)

* Add required under optional in group

* rename to field

* Fix other tests

* Check required field provided

* Fix all_required_children_are_set

* Fix tests

* Use if checks instead of try..except

* Add routine to check required fields for repeating groups

* Delete temporary file

* Fix path in data dict test

* Fix tests

* Cleanup

* Remove debugging line

* Add collector class

* Remove commented lines

* Check validation return type and logging

* Add tests for repeating groups

* Fix report of variadic groups set to all None

* Fixes undocumented units and reporting of all none required groups

* Use dict paths everywhere

Author: domna