Reset counters (NVis, etc) when removing actors from filter list.
Reset counters (NVis, etc) when removing actors from filter list.

Fixes problem where, when loading a different ref, the old number of
visible atoms would remain on screen.
chrisdjscott/Atoman,chrisdjscott/Atoman,chrisdjscott/Atoman,chrisdjscott/Atoman,chrisdjscott/Atoman