k-epsilon model

[katyhuff]

From @lindsayad :

The k-epsilon turbulence model was never finished since it really required SUPG stabilization to be relevant. Now, SUPG and PSPG are implemented in the navier-stokes module. So the k-epsilon model could be finished if someone wanted to work on it. It's very close to completion; the major piece remaining are the wall functions.

While Dr. Lindsay is not able to work on this directly, consult with @lindsayad to get appropriate initial direction.

[katyhuff]

fail. I meant this to be in the moltres repo... yikes. reopened in arfc/moltres#57