Streaming powstream measurements

[laeti-tia]

In the case we're refactoring or rewriting powstream to decrease resource usage, it would be interesting to provide a way to make streaming measurements, i.e. to not only rely on the one-minute batch file containing results but provide an API to send and receive results as soon as they're done.

Having such a functionality would be useful for external projects like microdep from SIKT (ex-UNINETT) to use the perfSONAR MP as source of measurements.