Refs #17059; merged forward and backward relations listing when having
the same title:

- Change: Merged forward and backward relations within eea_relateditems.pt in
  order to avoid having duplicated titles if both the forward and backward
  categories have the same title. If they don't have the same title then the
  behaviour will be the same as before this change.
Refs #17059; sort the relations result only within forward_backward method in order to avoid waisted computation
Refs #17059; added tests covering the logic of relations macro
Merge pull request #4 from collective/merged_relations

Merged forward and backward relations