Make Final standings calculator modular and extendable

[DanWasmer]

I'd like to make PGSwiss capable of doing standard SoS or Cumulative SoS, preferably on the same tournament result set. I can handle the new scoring calculator, but need a way of easily slotting it into the existing results framework.

[ThatRickGuy]

Add your new score type as a property on the doPlayer class in PGSwiss.Data.