5.2.0

• Added a (synchronous only, for now) path index implementation to the TermIndexing namespace.
• Made some minor changes to discrimination trees:
  • Some additional argument validation (just null checks) in a few methods
  • Added a Contains method to DiscriminationTree<T> and AsyncDiscriminationTree<T>
  • Made AsyncDiscriminationTreeDictionaryNode<T> thread-safe
• A couple of minor additions in the SentenceManipulation namespace:
  • Added some more public methods to Unifier class - with Term-valued arguments
  • Added sentence and term transformation interfaces that work with external state - ISentenceTransformation<out TOut, in TState> and ITermTransformation<out TOut, in TState>.
• A number of type and member documentation additions and improvements