new feature: let addons also add entity turns and resources

[PatrickHechler]

• add send/recieve turn/resouce methods to the addons interface (potentially create own interfaces for them (like AddonEntities))
• delegate to those methods in turn:sendTurn/retrieveTurn and OpenWorld:writeRes/RemoteWorld:readRes
• create a non-sealed MyEntityTurn abstract class and make EntityTurn not sealed
• make all Resource implementations not sealed and not enum (and make the interface not sealed)
  • this allows addons to add new resources to existing resource types (for example a new ore)
  • create a ResourceData interface which has a Resource type and a amount (and potentially some additional data)
    • this allows creating more complex resources like messages