JSON input of arrays of parameter lists

[Neil Carlson]

While one can manually create parameter values that are arrays of parameter lists through existing calls, it is not currently possible to create such things from JSON text input, which is a needed capability. The current limitation was a concession to simplicity in constructing array values during parsing, where only one array is being constructed at a time. If arrays of parameter lists, which themselves may contain arrays, are allowed, then multiple arrays may be in the process of being constructed at any moment during parsing. This requires a more complex stack implementation. This has since been done in the json.F90 module.