Accept/parse QuakeML from GEOFON to produce input for a new run

When a new event occurs, we can query the GEOFON fdsnws-event web service to get event parameters, including focal mechanism if available.

Angelo:

Peter to work with Riccardo in preparing the input which will be as simple as possible for the moment (yaml/json) including EQ Lat/Lon/Depth/Magnitude, and as soon as available the focal mechanism

This merge request does the query, parses the XML, and produces a basic Python structure. This can be easily serialised in the flavour of your choice.

For example, here is the YAML output for a large event in Greece: gfz2021eksc:

date: '2021-03-04'
focalmechanism:
- dip: 48.75643809
  rake: -91.74289876
  strike: 146.5577511
- dip: 41.27378495
  rake: -88.01325753
  strike: 329.2004058
id: gfz2021eksc
magnitude: 6.278409404
origin:
  depth: 10.0
  latitude: 39.79063416
  longitude: 22.28781891
preferred_focalmechanism_id: smi:org.gfz-potsdam.de/geofon/FocalMechanism/20210304185910.015761.20
39019
preferred_magnitude_id: smi:org.gfz-potsdam.de/geofon/Magnitude/20210304185910.01602.2039021
preferred_origin_id: smi:org.gfz-potsdam.de/geofon/Origin/20210304192045.9955.2520068
time: 18:38:20.19439Z

There are two (dip, rake, strike) sections for the two nodal planes. The QuakeML doesn't help us decide which to use.

From here, some integration will be needed to use the YAML to drive a run of the shake map.