PIVA viewer: Link all z-axis sliders

[lesslogic]

In 3D data view, link the z-axis (out-of-page) sliders across all plots. In other words, in a kx-ky map, change the energy in unison across all plots by dragging any energy slider. This would make the behavior consistent with the other sliders, and thus more expected. It will also make it clear which energy (or whatever is the z-axis parameter) is being viewed in the main map.