Fixed Constraints

Getting constraints working was super annoying. Basically, there is a problem where the engine is built around models, and you can spawn in multiple models. When models are spawned in, the parts inside are cloned including their IDs to not lose reference, but this comes with the huge issue as in the backend, the engine actually flattens this structure for more efficient processing of entities, meaning that there will be multiple entities sharing IDs, which is really bad.

But creating new IDs is also a huge problem because when we reference it, the ID is not final and changes all the time on load. So instead it does <model_id>:<entity_id>, for targeting.

The constraint creator lets you select two points (snapping will be added in the future) and it creates a constraint. This is later processed by the PhysicsSystem detecting the ConstraintComponent. Later there will be debug viewer for constraints.

Anyway it was just a lot of annoying work.