Changed DSUN_METERS to 1AU in meters. DSUN is not diameter of the Sun, but distance from observer to the feature. (defaults to 1AU)
Added transform function for Heliocentric(Cartesian) coordinates to Stonyhurst Heliographic coordinates.
Calculated B0 from heliographic_solar_center().
Calculated Heliographic parameters from formulae in sunpy.wcs.