Change dots size

Form the client

_Ability to scale the size of the cells, smaller or bigger to help visualization. The
currently selected size should be displayed._

So in the 3D viewer they would like to be able to change the dot sizes (i.e. neurons) because when there are too many neurons they can't really see well. I would set 3 or 4 fixed values, I don't think there is an interest in making the dots bigger than what they are now, but smaller. So the current size would be the biggest, then we could add a menu somewhere to make the dots smaller.