Followup to commit 0ff63e4f improvements in AssociationWidget :

umbrello/umlwidgets/associationwidget.cpp
- In function findInterceptOnEdge implement TODO note "try replacing by
  intersect()"; to be precise, use the Qt5 QLineF function intersects().
- In function updateAssociations foreach-loop over list,
  - continue to next iteration if (assocwidget == this);
  - add local Uml::Region::Enum regionAdjustedToRole = region;
  - if startsAtOther is true then flip regionAdjustedToRole such that
    North becomes South, West becomes East and vice versa;
  - on calling findInterceptOnEdge() use regionAdjustedToRole in lieu of
    region.