Implement ratio strong typing

[anders-wind]

In https://www.youtube.com/watch?v=5dhFtSu3wCo Chip Hogg describes that in their strong type library they have built in support for scales and ratios. Furthermore, just like chrono defines different ratios (seconds, milliseconds, days etc. ) as different types with conversions, we wish to implement a system to make this behavior easy to implement

[anders-wind]

Also their approach to the typelist is a bit more elegant. Essentially, instead of repeating the same units multiple times they have <unit, power> to represent: unit^power. This makes a number of operations more efficient (just subtract instead of having to remove each one of them).