Add error reporting

[khawkins98]

We had an incident where some of the source fcgi scripts were not providing data (timeout), this was causing the map's JS to "clog" up the browser CPU and RAM.

We now avoid that with a timeout in the JS.

That fixes the symptom, but we need to know when the map isn't getting the data it needs.

Do we have prefered error reporting solution?

[khawkins98]

There is a conversation stub at: https://embl-ebi-developers.slack.com/archives/C4WU8THSM/p1502791138000076