Lights, Audio, UnitValue and associated properties

[mikeapp]

Questions:

• intensity and volume - restrict from use on other resources?
• Note about Spot Audio requiring a transform. I changed to default to -y direction, like Spot Light.

[JulieWinchester]

I wonder if maybe -Z makes more sense as a default direction, like a camera, rather than -Y like a light? I'm sort of analogizing a spotaudio source to kind of like a directed speaker, which I think might be more natural to have in the same XZ "horizontal" plane by default, pointing "back" at me, rather than pointing "down" at me? Interested in what others think, though.

[mikeapp]

I'm assuming that for Audio source we'd want to allow at least Timeline, and possibly any Container (i.e., an implicit selection of the audio track from a Canvas or Scene). I assumed this was covered by "Containers may be treated as content resources for the purposes of annotating on to other Containers." but it relies on a loose reading of "annotating on to". This might need to be called out in property definition.