Handle stale / offline webcams

[mttchpmn]

• Handle when a webcam goes offline, or is not updating quickly
• Perhaps set a 'stale' flag or similar in response from API

[mttchpmn]

Perhaps in loadAll.js add a check to get all webcams from last 24 hours, but ALSO to check that there's also cams from at least the last 6 hours (or 3 hrs), and if not, then don't return any images in array.

Front end can handle by checking to see if images array.length prop > 0

Equally, we could also add a stale: true flag to the response object (this may be most robust)

[mttchpmn]

We shouldn't drop cams from the response just because they are stale, as front end may want to display them regardless, and just show an icon to denote they are stale temporairly