Support for DFUInfo

[dcamper]

This is a request to add support for the WsDFU/DFUInfo service call, with full support for all return values. The call can be read-only (no support for updating the description for a file is needed).

The eventual goal is to support generation of ECL's RECORD and DATASET declarations, given only the name of an existing file on a cluster. Both declarations can be fully populated from the result of a successful DFUInfo call.

[GordonSmith]

@dcamper FYI this project has been rolled into a new "hpcc-js" namespace, which in turn is an evolution of Visualization (but will get renamed prior to the 2.0 release).

The current sources can be found here:

• https://github.com/hpcc-systems/Visualization/tree/candidate-2.0.x/packages/comms

DFUInfo has not been implemented yet, but it is on the todo list as most of the comms layer in ECL Watch will switch over to this new library.

[GordonSmith]

@dcamper - here is an example of what you can do today: https://beta.observablehq.com/@gordonsmith/fetch-ecl-record-layout-from-logical-file-name