Change operation version in network after setsource?

[jonnor]

Right now, when changing the source code of an operation, we build & load the new operation version into component library. But we don't change which revision is used in the active network (until it is restarted, or component is readded), which might be unexpected.

We could do this by iterating over nodes, and calling gegl_node_set(node, "operation", new_op, NULL) on those that need updating;