10 fix atmosphere bar

[tcannonfodder]

Tweak atmospheric gauge to try to use logarithmic scale

• This partially makes the atmospheric gauge behave more like the in- game one, but it's still incomplete.

Thanks to https://www.reddit.com/r/KerbalAcademy/comments/4qpgv2/what_is_the_math_behind_the_atmosphere_gauge/

This partially fixes #10