1. Partial coherence module built and tested, fits a Gaussian blurrin…

…g kernel

(S. Maddali et. al., Phys. Rev. Applied 14, 024085, 2020)

Incorporated Gaussian partial coherence correction

1) Fixed error in which recipe parser plugin was not included in GPUM…

…odule core.

2) Tweaked README.md section on recipe strings.
3) Added acknowledgements