Fix missing relations

[metmirr]

This PR fixes #443.

Problem Relation generator adds visited fields into a Set in the field.name:relatedField.name. So if there are two relationships with the same name across entities one of them will be missing due to the bug.

Fix The bug is fixed by including entity and related entity names in the unique key generation: entity.name-relatedEntity.name:field.name-relatedField.name

affects: @joystream/hydra-cli