Parsec isochrones

[mkounkel]

Added Av coefficients for bands that isochrone breaks if distance is included

Compiled some photometry from parsec isochrones

[timothydmorton]

Thanks for this effort! The current development branch is bolo, which will become the v2 release, so we'll have to recast this in that new formulation, but including parsec isochrones is a great idea.

[mkounkel]

It is almost entirely copied from MIST isochrone package, with only the loading of the grid modified for it to function.