Add a mouse-over pop-up of "Number discharges upstream" on the downstream sections

[AlexLipp]

Users have communicated that they often manually count the number of active discharges upstream of a given point. Whilst they seem happy to do this, it would be relatively easy to automatically display this as a mouse-over pop-up. This can be achieved by calculating and returning the # of discharges upstream as a multi-point geojson file in POOPy, with the values stored in the properties. This will then need to be visualised on the map.

[AlexLipp]

A potential additional extension would be: A list of the names of all the sources upstream of a point.

[AlexLipp]

I have updated the back-end to create a FeatureCollection geojson which contains this information. The CloudFront URL for this file is: https://d1kmd884co9q6x.cloudfront.net/info_now/info_now.geojson.

This FeatureCollection contains as features multiple Points as features. Each feature has the same structure, for example:

{
    "geometry": {
        "coordinates": [-1.301724631322461, 51.91449148223558],
        "type": "Point",
    },
    "properties": {
        "CSOs": [
            "Avon Dassett",
            "Boddington",
            "Chacombe",
            "Chipping Warden",
            "Eydon",
            "Farnborough (Warks)",
            "Wardington",
        ],
        "number_CSOs_per_km2": 0.01314405888538373,
        "number_upstream_CSOs": 7.0,
    },
    "type": "Feature",
}

The Properties of the points contain the relevant information: 1) How many CSOs are upstream of that point on the river; 2) This same number divided by upstream area (e.g., "density" of CSOs), and 3) the list of what CSOs are upstream of each point.

Hopefully you can come up with some useful way to visualise this! Let me know if you'd like the data provided in a different format!

[AlexLipp]

Downstream info data for all water-companies is now available as per new issue #26