easy access to DatasetUtil.get_set_flags()

I think getting access to what flags are currently set is very useful. This is currently possible with:

from obsarray.templater.dataset_util import DatasetUtil
print([DatasetUtil.get_set_flags(flag) for flag in data["quality_flag"]])

However I think this functionality is so useful that it would be great if it would be more easily accessible. Maybe we can write a little wrapper around it?