Add example parameter sweep code examples for preconditioning and gradient quality

[jgoldfar]

The optimization code required a bit of reorganizing, but the code now includes feature flags to adjust the preconditioning and other parameters of the reconstruction without having to make more significant changes

[jgoldfar]

I think this is working relatively well now; two examples are added:

• gradientQuality.m and its driver plot_gradientQuality.m demonstrates how to add some ancillary calculation and automatically create data files appropriate for importing into any plotting program (including back into MATLAB)
• plot_precondEffectS.m demonstrates how to take the output of an existing script, post-process it (by taking norm declination) and generate an output file and possibly plots as above. The extension to 2D parameter sweeps is left as an exercise, though for the output file format I would suggest an option here or here