Allow users to specify longer timeouts for time series requests.

[tmcphillips]

We should allow people to override the server timeout and be willing to wait longer (maybe a minute) if they really want a larger area.

[tmcphillips]

The timeseries service currently supports this feature using the timeout GET/POST request query line parameter or the timeout JSON property in a POST request body.

The timeout set on the server (via the TIMESERIES_MAX_PROCESSING_TIME environment variable) serves as a maximum for any request. However, the client can specify a shorter timeout in each request. So we could configure the max on the server to 5 minutes, say, and provide a user-configurable timeout in the web interface that defaults to something like 15 seconds.

[kintigh]

That would be ideal. I suppose there could be a settings option at the top right of the screen, or IF the server timeout happens, one could be prompted to change it, or both.