Use HAPI info as a LaTiS dataset descriptor

[dlindhol]

The de facto technique for describing a dataset in LaTiS is FDML. For data providers setting up a LASP HAPI server, it would be easier if they could use the more familiar HAPI info JSON response format instead of having to learn the FDML (XML) syntax.

We already have a HapiReader which constructs a Dataset using the HAPI info response. We should be able to build on that to use locally managed JSON files as dataset descriptors (akin to FDML files).

The HAPI info content is not exactly what we need, but we should be able to support something that is largely the same, especially when it comes to the parameter definitions. We would need to add the source URI and adapter information.