QGraphicsTextItem supports only external links when clicking on a
hyperlink

In addition to the substitute command (s,from, to,[g]) it is possible to
limit the search/replace to specific symbols, in order to refactor the
namings without touching other symbols.
For example: %state,from,to, will change only the text in the state
symbols

%s,from,to,g -> g is global across all scenes

1) translate_to_origin was using symbol coordinates instead of scene
coordinates so there could still be negative coordinates
2) render_everything was badly testing the input ast coordinates