Plan: Spatial Datastructures as Entities

[laundmo]

I'm planning changing this library to store spatial DS as entities instead of resources.

changes:

• plugin not generic anymore
• user can decide between different update modes by adding a system
  • this system is a static method on the DS
  • this system is generic over the marker component, to know what to query for
• allow for less macros/traits - multiple updater-systems instead
• easier scheduling by user adding the updated system themselves, can easily order it.