Return status code for long run process.

And add function to log resource usage.
Add timer to update message during server processing.
Add data source date field in police station model.

And use this field to filter police station query, if we have police stations
populated from mulitple raw data in the future.
Move model-specific constant value into model itself.
Remove police statations from same data source date only.
Rework police station entities.

1. Make all police station entities populated from the same raw data within
   the same entity group. (Use data date as key)
2. Make police station entities population and clean up in transaction.
   (Write all or write none, delete all or delete none)
Remove show police stations from dashboard.

Now police station entities list can only be accessed from raw police station
data page.
Add publish/unpublish function.
Change id to class.
Fix typo.
Add api for opendata: published police stations.
Fix bug.