Enable tuning of relationships to consider in SMengine

[sharispe]

The aim of this enhancement is to be able to tune the relationship to consider when creating an instance of SM_Engine. Currently SM_Engine only consider rdfs:subClassOf relationships for computing semantic measures. However, it could be nice to load the engine by defining another transitive relationship, e.g part-of relationship and therefore be able to use a measure by considering this specific type of relationship. It could also be interesting to enable the consideration of multiple transitive relationships - but this makes the development and tuning more complex since the expected way to handle paths composed of relationships of different types must also be specified.

[sharispe]

This has been integrated to SML lib.
Additional modifications have to be made to be able to use this modification from the toolkit.