Web: Support ONVIF event types

[curtishall]

Part of #662, allow the web UI to poll the camera to see event types...these should (always?) be in located nested in the /RuleEngine response:

EVENT: 2024-02-21T00:59:55.000Z RuleEngine/CellMotionDetector/Motion PROP:Initialized SRC:VideoSourceConfigurationToken=000 DATA:IsMotion=false
EVENT: 2024-02-21T00:59:55.000Z RuleEngine/MyRuleDetector/FaceDetect PROP:Initialized SRC:Source=VideoSourceToken DATA:State=false
EVENT: 2024-02-21T00:59:55.000Z RuleEngine/MyRuleDetector/PeopleDetect PROP:Initialized SRC:Source=VideoSourceToken DATA:State=false
EVENT: 2024-02-21T00:59:55.000Z RuleEngine/MyRuleDetector/VehicleDetect PROP:Initialized SRC:Source=VideoSourceToken DATA:State=false
EVENT: 2024-02-21T00:59:55.000Z RuleEngine/MyRuleDetector/DogCatDetect PROP:Initialized SRC:Source=VideoSourceToken DATA:State=false

Then modify the web UI schedule to support selected types