2D Gaussian fitting macro (Fiji/ImageJ) for multiple signals.

This script includes a rough feature detection and then fine 2D Gaussian algorithm to fit Gaussians within detected regions.
This macro is unique because the ImageJ/Fiji curve fitting API only supports 1-D curve. I get around this by linearising the equation.
This implementation is for isotropic (spherical) or anistropic (longer in x/y) diagonally covariant Gaussians but not fully covariant Gaussians (anisotropic and rotated). Based on https://en.wikipedia.org/wiki/Gaussian_function