Make HLSMonitorService API a bit more restful

[birme]

This is not a critical issue of any kind but I think it could be worth making the API that the HLSMonitorService provides a bit more restful. I propose the following resources and methods:

Endpoint	Method	Description
/	GET	Heartbeat endpoint of service
/monitor	POST	Create a HLS monitor. Provide JSON body with streams to monitor
/monitor	GET	List all active monitors
/monitor/:monitorId/streams	GET	List all streams a monitor is monitoring
/monitor/:monitorId	PUT	Update what streams a monitor is monitoring. Provide JSON body with streams to monitor
/monitor/:monitorId	DELETE	Delete a monitor and stop monitoring the streams