Started working on relevance function
Fixed compilation errors and added code for testSimilarityNull
Changed Query to QueryType interface in similarity argument and added tests for similarity when either the document or the query is empty.
Fixed tests and added code for similarity function
Added IndexedDocument and RetrievedDocument classes
Replaced HashSet with ArrayList for getAllNodes and getNodeEdges - there is no need to be hashing the objects in the returned collection
Added equals and hashCode methods to IndexedDocument, with tests
Added InvertedIndexBuilder with tests
Added code for InvertedIndexBuilder methods
Added getIDFWeights function and an IDF weights argument to the similarity function, altering tests accordingly
Added code to deal with IDF values to similarity function and fixed tests
Added tests for getIDFValue
Added code for getDocumentCount and getIDFValue, and fixed tests
Added test for getIDFWeights and committed missing hasTerm interface function
Added code for getIDFWeights