Essentially thermistor_interpolator is now where it should have been before I released v1.1:

1. More and improved checks on calculation results throughout the routine
2. End-to-end accuracy test of new operational mode (NTC defined by .csv file of temperatures /resistances) passed
3. Removed some latent debug code...

Other minor touchups:

1. Passing iterator arguments by const reference instead of value in iterator-based GCD() and LCM() variants
2. Use of type aliases to make RCSn less unreadable