HAPI: Change x_maxTimeSelection to maxRequestDuration

[smithara]

The HAPI spec version 3.1 added maxRequestDuration to the dataset info response. This should replace the x_maxTimeSelection that VirES is currently using.

Two other optional items were also added to the info response in v3.1: coordinateSystemSchema and additionalMetadata. I am not sure if we are ready to adopt these yet

[pacesm]

Thanks for the report. I'll have look on it.