Refs #10302 Add getUnusedGroup
Refs #10302 Make inserted use new group ids
Refs #10302 Make add row append a single row
Refs #10302 Update unit tests
Refs #10302 Update indentation
Refs #10302 Merge indentation commit

This avoids conflicts with #10295.
Merge branch 'feature/10302_refl_ui_row_management' into develop