Add an "Add Molecule" + button

[matterhorn103]

A new layer can be added from the Layers Pane by a simple click on the + icon; an analogous button in the Molecules Pane would be a simple addition that would help interface consistency.

As they are similar in appearance and location users will likely expect the Layers Pane and Molecules Pane to work in similar ways.

While it is already possible to add a new "Molecule" via File => New or by clicking New on the toolbar, the fact that "files" and "molecules" are essentially the same thing in Avo is not explicitly clear and users may be left wondering how to add a new entry to the list.

[ghutchis]

This would actually be in avogadroapp... transferring.