Add a boolean input to the gizmo nodes to control visibility

Gizmos are so useful that I want to add them to all of my node trees. But many of my node trees are fairly complex, with menus controlling which UI elements are visible and used and which are hidden.

Gizmos, however, do not respect this show/hide feature of the actual input elements and are always visible. And even if they did, it would be useful to be able to control their visibility from within the network (without having the have the end-user dive into the network).

I propose that a boolean input be added to the gizmos that would control their visibility.

By default the box would be checked, but unchecking it as in the image above would render the gizmo invisible.

By making it an input, all of the regular logic that we have to control a node network could also be used to control gizmo visibility.