Function distanceEstimateEdsd( plxMas, plxErrorMas, lPc )

Description:
Best estimate of distance using the Exponentially Decreasing Space Density prior. This estimate is provided by the mode of the PDF.
Parameters:
plxMas (floating point)
parallax in mas
plxErrorMas (floating point)
parallax error in mas
lPc (floating point)
length scale in parsec
Return Value (floating point):
best distance estimate in parsec
Signature:
double distanceEstimateEdsd(double, double, double)