Particles offset & scale

This pull request address a small issue with particles and scaling and also adds a new option to allow you to define where the origin of the particles should be placed.

When the component was calculating where it should render the particles and the size of them, the viewport current _scale wasn't being taked into account, so if you zoomed the viewport, the particles place & size were incorrect.

Also, I've added a small option to allow users to define where the origin of the particles should be, allowing them to add a offset to the position of the particles' parent object.