Push observations

[abkfenris]

Support pushing observations directly to Buoy Barn from Sea Eagle, and in the process allow moving to a more reconciliation loop-like (via video example) model which may be easier to understand when things go awry.

New routes:

• Get /api/timeseries/
• Get /api/timeseries/{id}/
• Get /api/timeseries/batch
  • Timeseries that are currently out of date, or have been otherwise marked ready for immediate updating
• Put /api/timeseries/batch
  • Update multiple time series at once
  • If an update is put without a constraint, but has a constraint saved on it, then it should be marked as ready to update.
  • Should be able to put timeseries without knowing the ID, and derive it from server + dataset_id + variable

Updated routes:

• Get /api/server/refresh
  • Sets Timeseries.update_requested to True for all timeseries on the server
• Get /api/dataset/refresh
  • Sets Timeseries.update_requested to True for all timeseries for dataset

New fields

• Timeseries.update_requested
• Timeseries.update_attempted?
• ErddapServer.update_period_minutes defaults to 1 hour, can be None for servers that should only update by pushing