replace xmlrpc++ #18
Description
The xmlrpc++ dependency is problematic. The library is no longer supported, and it is not available as a system package on NIDAS targets. ISFS does not use it currently, so ISFS might benefit from just compiling it out, to simplify Raspberry Pi packaging. Or, we could replace it, either with a different xmlrpc implementation, or a different RPC implementation, like gRPC or boost.beast, or with a messaging system like ZeroMQ or AMQP or MQTT. I am leaning towards a messaging system, so a DSM can publish more kinds of status and data without needing to handle connections from consumers.
Further, the RPC API currently served by the dsm process returns html excerpts. It should instead return data in json or xml according to a schema, then the rendering to present the data can be implemented where needed. NIDAS should not have code to printStatus(), and the DSMSensor class especially should not have a flag for zebra striping!