Added a preliminary version of "DataPublisher"

Created by: marcus-oscarsson

The DataPublisher contain DataSources(s) that publishes data to a listening client. The data is published through Redis and can thus be used in a distributed system. So the results can be generated on a computer different from the computer hosting HWR. It further provides a convenient way to get the data back if the client/server crashes or disconnects while scanning

The UI needs to listen to the start, data, and end events and provide a component that can display the data.

This can perhaps be extended to handle any underlying message queue system but I waned to avoid the complexity for now. What we needed was a central place through which we send plot data or other data to the client and a convenient way to access any "unsaved" data in case of a problem.

Marcus