Bugs/enhancements for ShOpt runs

[mcclearyj]

I ran into the following issues when running ShOpt for the first time.

Bugs

• [x] dataPreprocessing.jl assumes VIGNET exists in HDU 2 of a FITS file. This is a very common issue; it would be nice if ShOpt handled this gracefully.
• [x] reader.jl looks for an extension that doesn't exist in the default truncated mode (3)
• [x] Star cutouts are off-center in "comfort plot" cutouts produced during run. Is this systematic? It could be minor but if that off-centered star is fed to the pixel grid fitter, that could propagate into the model and cause real problems down the line.

Suggested enhancements

• [ ] It would be nice if one could supply other config files to ShOpt. Half the point of using configuration files is not having to change the same file for different use cases.
• [ ] Not a bug, but the polynomial degree of the analytic (Gaussian) profile fit should be a tunable parameter. At the very least, it should match the pixel grid fit polynomial degree.