Opendatasoft - support pagination/increase number of rows

[nf-s]

Currently Opendatasoft will only request 1000 records - this because the limit per request is usually 100 (if no groupBy operation is used), and we do 10 requests.

This is not configurable, and there is no way to trigger Terria to load more records.

Some thoughts

• Use export endpoint for some datasets - then we can just request the entire thing as CSV or GeoJSON
• Add "load more" button...
• Make maxRecords a trait, so we can bump it up if we need too
• ...