add option to specify the data source in the monitor widget

In particular, "scan_segment", "redis" and "history" would be good to support

{"source": "scan_segment", "name": "bpm4i", "entry": "bpm4i"},
{"source": "redis", "endpoint": "<endpoint>", "update": "append"},
{"source": "history", "scanID": "<scanID>", "name": "bpm4i", "entry": "bpm4i"}