Incorporate bathing water quality testing data

[AlexLipp]

Bathing water data is now available at Wolvercote and Wallingford during the summer months. The data is available via an API. This data could trivially be included in the SewageMap data display and would provide helpful additional data for users.

[hagrid67]

Could also consider adding the slightly more numerous "citizen science" testing records from Water Testing River Thames.co.uk
Could also look for some some relationship between outflow events and downstream pollution measurement to help calibrate / train an advection / mixing model.