webGIS: add option in settings.py for max event query size

[megies]

Currently hard coded at 20k and rotations DB is over that already. Should be configurable in settings.py

jane/src/jane/static/web_gis/src/baynetapp.js

Line 51 in 7322d77

var url = jane_server + "/rest/document_indices/quakeml?limit=20000";

CC @heinerigel