Hack fix: Gas giant atmosphere workaround+increase 0 K workaround temp+set atmosphere density default values, and avoid unphysical default temps

Before I forget.. Quick gas giant workaround.

Since the gas giant surface represents the actual atmosphere, adding an atmosphere on top just hides the details.

The gas giant scale heights are fixed in the WiP PR-ed part of the atmosphere branch, but the complete atmosphere submission will not be ready very soon.

This is a temporary solution.

Very thin white atmosphere to avoid obscuring surface. Visible near the surface.
![](http://i.imgur.com/GTe2b.png)

![](http://i.imgur.com/9tZoP.png)
The scale height and gas giant colour alpha can be tweaked to increase atmosphere size and density, if anyone wants to tweak further.