Search for similar values

Add a way to search similar string values using Jena full text search. Lucene already has the implementation. Similarity would be between single triple values, not entire resources.

So for triples

:r1 rdfs:label "This is an example string".

:r2 rdfs:label "This is also an example string" .

:r3 rdfs:label "something else" .

similarity query

:r1 rdfs:label ?label . ?s text:similar (rdfs:label ?label)

would return :r2 with highest score.