Do not delete Explosion objects outside of Workspace

Currently, if you place an Explosion object anywhere in the DataModel, it will immediately be destroyed after exploding.

Although it’s also possible to make custom explosion effects using your own ParticleEmitters/Sounds/BodyMovers, it would be nice if explosions could be templated (e.g. placed in an “assets” folder), since they offer easy physics and visual/audio effects that can be toggled

I think explosion objects should only be deleted when placed in the Workspace, or with a newly added property that controls whether they will be deleted.