add service monitor to monitoring page

add service monitor to monitoring page

monitor endpoint and database change

add monitoring page to ATDB

- moved order of columns in dashboard
- some visual improvements (hopefully)

SDC-470: Create api-function to retrieve the minimum start time and maximum end time for a given sasid

https://support.astron.nl/jira/browse/SDC-475

(and to read serializer, not yet to write serializer)

Keep state of the query fields in the Query page when a SetStatus button is clicked (also for multi set status)

http://localhost:8000/atdb/tasks/?predecessor__isnull=True

added /atdb/tasks/?predecessor__status=defining filter options to REST API

add 'resume' filter (hold/start)
removed 'defining' filters
added nicer 'Filter' button