friendly-coins Rule #5: No Abbrvs

For this refactor I renamed a few classes and a relative lot of variables and fields.

It felt good. I kind of felt like I had just taken a nice hot shower after swimming in the Charles.

Not only did I get rid of abbreviations, I also renamed after thinking a bit about what a meaningful name would be, and I also tried to standardize naming.

So, whereas MinNumCoinsSolver became MinimumCoinCountSolver (abbrvs),
many instances of “greedySolution” became “highestFirstSolution” (because the class that produced them had always been named HighestFirstSolver).

I also split the “Helpers” class into several different types of helpers: Again, this was not merely watching out for abbreviations, but also paying attention to reasonable naming and even packaging (a prelude to Rule #6)