Add Star Creation Easy Mode

[frodre]

Right now star creation lets you create situations that are outside of the commonly found (or even possible) star/rocky-planet systems. We should also provide an easy way to keep the star on the main sequence.

• Create a tabbed widget box with 'Easy' and 'Hard' mode star creation.
  • Easy mode should be the main sequence where the effective temperature and luminosity are controlled by the radius. Based on Michael's calc: T = T0*(R/R0)^(9/8) where T0, and R0 are reference values. (What is the reference?)
  • Hard mode should be the original luminosity and temperature sliders