Particles don't fire again when unmarking "One Shot"

[YeldhamDev]

Ubuntu 17.04 - Godot version: 3.0.alpha1

Issue description:
When unmarking the "One Shot" option in a Particles/Particles2D node, it will not start firing again unless either the scene is restarted, or setting off and on the Emitting opition.

[ISylvox]

I think it's expected. That is the point of One Shot.

Emitting ON + OneShot ON will play the particle only once during its Time/Lifetime and then Stopped. To play the particle again, need to restart Emitting.

[kubecz3k]

I think it could be fixed, there is no reason why this should not happen transparently for the user. Presentation from the actual issue:

[kubecz3k]

I'm not sure but this probably should not be hard to solve (hence junior job)