BUG: extendedFeatureEdgeMesh: Swap feature point algorithm for a faster one

The population of featurePointFeatureEdges was slow. Added a List called
edgeMap that contains the featureEdge index for every edge in a patch
(returns -1 if it is not a feature edge).
BUG: extendedFeatureEdgeMesh: Prevent division by zero when normalising edgeDirections