SystemUpdateID event

[CraigD]

My control point is still under heavy development - but if you are interested the code is at https://github.com/CDrummond/madrigal The CP is built using the Qt5 libraries - and should compile for Linux (which I use for development), Windows, and Mac (but I'm not regularly building for Windows or Mac, so can't guarantee it will always build)

I'll look into the idea of preserving the path - but this is not going to be 100% reliable, as tags could be changed, and the upnp IDs are not guaranteed to be unique. Not sure its worth the hassle - as I doubt the DB changes often.