Clarify visibility annotation in DiatomicMoleculeNode

[zepumph]

from code review #30
I'm confused about this comment before a batch of node declarations:

// @private nodes whose visibility may change
this.partialChargeNodeA = PartialChargeNode.createOppositePartialChargeNode( molecule.atomA, molecule.bond ); // @private
    this.partialChargeNodeB = PartialChargeNode.createOppositePartialChargeNode( molecule.atomB, molecule.bond ); // @private
    this.electrostaticPotentialNode = new ElectrostaticPotentialNode( molecule ); // @private
    this.electronDensityNode = new ElectronDensityNode( molecule ); // @private
    this.bondDipoleNode = new BondDipoleNode( molecule.bond ); // @private

Could you be a bit more specific. I didn't realize visibility annotations could change throughout the lifetime of a sim. If I'm just ignorant please inform and sorry to both with another issue.

[pixelzoom]

You're confusing visibility of Nodes (whether they are rendered) with visibility annotations.

I've removed the confusing comment. @zepumph please review.