Remodel HeadwayJourneyGroup

[skinkie]

    <xsd:group name="JourneyFrequencyGroupGroup">

has a choice - sequence, this one of the worst combination, investigate what should be done to make it usable.

[ue71603]

Stefan tries to remodel it.

[Aurige]

Since the first element of each sequence is mandatory, this should not be an issue ... but I agree that choice of sequence should be avoided