Relation History tidy

I was looking to use this but with a bit more testability. I modified mostly the interface to look/act more like a standard container, including having iterators (so we can use standard algorithms for simplicity), etc. I also pulled out some components that depended only on the max size to avoid excess template instantiations, simplify the code (you have to be able to compare an iterator with a const_iterator), etc. There are also tests now for the underlying c++ templates.

Thanks for the great start on this @slitcch ! If you have questions about the techniques I used to revise this feel free to ask.