[NO MERGE] Contextual Data API

[aromaa]

Sponge | SpongeAPI

Open questions?

• [ ] Server as DataPerspective? One could implement way to hide specific entity data like health from clients globally.
• [ ] This could also be used to change the world properties send to the client like weather by taking advantage of the World -> Entity data direction. Do we want that?
• [ ] How do we implement collection operations? What happen happen when you do offerSingle to the data perspective and the base entity already has elements. Append? Create new list with just that single item?
• [ ] Do we want to allow plugins to provide more info how to solve merge conflicts?
  • [ ] Provide types to provide the operation type? Like Value<Integer> could have addition, multiplication, etc.
  • [ ] Allow that same concept for values with collections?