Fix min peak references and add command-line option

[nicholasprussen]

• Make min-peak in GaussianFitter a command-line argument, default 10
• Verify correct usage of min peak in guess_peaks GaussianFitter.cpp:740
• Verify correct usage in find_peaks GaussianFitter.cpp:398
• Test if "Amplitude OOB" spdlog ever flags, GaussianFitter.cpp:399