 * Cleanup differential rotation/rotational mixing in code

 * Convert scheme for calculating fp and ft to fully implicit (may need an extra
   equation for the psi integral)

 * Fix detection of presence of symbolic links. Right now, it doesn't work
   properly for overriding output fort.nnn files.

 * Cleanup the code. In particular, make things like cfuncs output their
   results in variables that are in a clear and "clean" place, rather than
   all over the place.
