Graph view for FDSN Event services and FDSN Availability services

It would be useful to add GRAPH view for FDSN Event services and WFCatalog services. Plot data in graph view as timeseries for the following services:

• FDSN Event: Plot magnitude of earthquakes against time (preferably as scatter plot, not continuous line)
  • Parameters of historical earthquakes (1000-1899) - FDSN event
  • Parameters of modern earthquakes (1998-present) - FDSN event
  • Other 11 FDSN Event services in NFO (historical and modern EQs)
  • Example payload (formats available: text, xml, json): https://www.seismicportal.eu/fdsnws/event/1/query?minlatitude=30&maxlatitude=90&minlongitude=-40&maxlongitude=50&minmagnitude=5&includeallorigins=false&includearrivals=false&limit=500&format=text&nodata=204
• WFCatalog service: Plot waveform data availability against time (one percentage value per day per channel; vertical ??Z channel only)
  • All EIDA nodes providing this service (currently 12 nodes + federator)
  • Example payload (geoJSON only): https://eida.bgr.de/eidaws/wfcatalog/1/query?starttime=2016-11-01T00%3A00%3A00&endtime=2016-11-23T00%3A00%3A00&network=GR&station=GRA1&csegments=false&longestonly=false
  • Possibly other quantities can be extracted for daily granules "start_time": "percent_availability", "sum_gaps", "num_gaps"

Notification: @Carlo.Cauzzi: The initially discussed FDSN Availability payload does not contain direct availability values but only time range/extent where the daa is available. This would require to calculate the actual percentage based on time. For this reason I opt for WFCatalog which has the percentage directly available at daily granules.