#82 OOBN nodes disappearing

[Rommel Novaes Carvalho]

When we change the view to an OOBN class that have instance nodes (frames), move a node inside an OOBN instance (frame) anywhere (before, when this was allowed), then we change the view to another class and then go back to the previous class, the nodes that should be inside the frames are now outside and disappear.

I think this problem occurs because of numerical differences between local (inside the frame) and global (inside the canvas) coordinates. The coordinates of the nodes inside the frames were using local coordinates. This problem gets worse as the global coordinate gets higher (further to t

I kind of fixed for now this problem by not allowing the user to move the node inside a frame, but this should not be the final solution. I tried to fixed it, but had some problems with the local and global coordinates. The node should be allowed to move just inside the frame, never outside.