Contrib Clock uses millisecond

[bashbash]

srschaff https://jira.jpl.nasa.gov/browse/AERIEQS-336 Moderate The model resource for Clock from aerie.contrib uses milliseconds, different than elsewhere in aerie that uses either microseconds or seconds. It would be much easier to use if everything were in seconds, or at least this demonstration Clock resource.

[https://github.com/NASA-AMMOS/aerie/blob/develop/contrib/src/main/java/gov/nasa/jpl/aerie/contrib/models/Clock.java#L13]

This easily leads (led) to confusion when trying to use those Clock resources in scheduling rules that must mix and match between microseconds (eg Recurrence goal interval), seconds (controllable duration parameter), and now microseconds (constraints on clock resource).