FeatureUnit documentation

Are there docs anywhere on the details of the FeatureUnit observation?

Unclear ones are
1. When does is_blip get used, and how does it affect other attributes? For example, what is the unit_type when is_blip is true?
2. What is the normal values for weapon cooldown? Is it a countdown until weapon is ready to fire again?
3. what are order_id 0-3? if its a build queue, what about order_id 4?
4. How do buff 0 and 1 work? For example if a banshee is cloaked and affected by fungal growth, which would be in which slot? what if there is a third buff?
5. Which buff does buff duration refer to?
6. How do order progress 1 and 2 work?
7. How does facing work?
8. What do mineral / vespene contents refer to? are they the remaining resource on a geyser or the minerals in the hand of a worker?

apart from those, I can't see any obvious locations where the scale of the properties are defined

@skjb I've tried searching through your code and blogs but haven't found any definitive answers, I'm hoping you or someone else can help me out.

Cheers,
Luke