Treat two links as a bidirectional link only when they share common resource, relation and confidence

E.g. link between w1 and w2, when there exists rules such as: w1->w2, WordNet synonym with confidence 0.5 and w2->w1, WordNet synonym with confidence 0.5. 
Otherwise it may cause loss of information, i.e. if w1->w2 from BAP is with confidence of 0.8 and w2->w1 from BAP is with confidence 0.1.