unified World.Query and World.QueryBuilder | reduced allocations on a…

… system run

disallow adding duplicate components, as this is potentially very dan…

…gerous

System as Interface, fixed a problem with removing relationships of d…

…espawned entities

API overhaul

stability improvements + global lock

stability improvements + ReplaceElement / AddOrReplaceElement

fixes and improvements

replaced ForEach(() => {}) with foreach (var () in query) {}

initial release