Fix so that a RelationLabels shows child relations as well as parent …

[Jeavon]

…for biDirectional relation type as currently it does not.

Also removed usage of Umbraco legacy references in GetRelationTypes method and refactored to use RelationsService

[Hendy]

Hi @Jeavon I don't suppose you can recall the use-case for checking for bi-directional relations ? (the parent is always the picked item, and the child always the context of the picker regardless of the relation direction - I'm making the assumption that the relation labels will always be on the picked item - or is this to take into account relations created though another mechanism ?)