[LWFXEF] Provide utility methods for placing curves and their labels
Use case 1:
When connecting ports of the same ellipse, a straight line is inconvenient. Instead, a default bend point should be introduced which results in a curved line ideally outside of the ellipse (see illustration). A utility method for providing this point would be useful.
Use case 2:
A similar method to the one described in use case 1 would be useful to place the label of a curve, using the returned point as the location of the label (including some offset).
(from redmine: issue id 3930, created on 2020-02-04)