preload classes to improve performance

When a user does not preload an atom lots of classes do
not get loaded and initialized.

Then, when the user clicks a button to load a molecule,
lots of classes get loaded into memory and there is
slow response.

See about preloading some classes in the case where
there are neither 'load' nor 'script' parameters.

Perhaps you can simulate/force this entire process by
doing a 'load' of some string constant that doesn't
really contain anything.