Scale support for volume shaders

Currently volume renders independently of object scale and density doesn't get affected at all. It makes it really hard to work with real-world dimensions like planet atmosphere (e.g. 4km width/height, 16km length) without having troubles with transparency. Using microscopic values have its limits too and can't be lowered to required <0.000001, because then rendering bugs appear. Last statement doesn't occurs with every volume shader though, but most wanted Volume Scattering. To be more precise what happens: scattering effect disappears and only Volume Absorption with inverted color stays.

To avoid this behaviour, I see 3 programmatically possible (as I think) ways in sum:

• Emission-like shader, as analog for semirealistic fog render at least. Extremely minimum values work with Emission and Absorption perfectly, but the problem with first is that shadows disappear (especially noticeably in night scenes), and the last is kinda opposite (doesn't suits case at all). Thus it's need to be somehow reworked internally, for accepting light inexistense and shadow drops.
• Full support for any lowest value in current Volume Scattering shader only.
• The title.

I end up with conclusion of third variant, because the first sounds like a workaround - not a real fix, and the second IMHO doesn't sound perspectively enough (but this can be argued of course, as I don't see any plans for adding new volume shaders anyways).