Added RegexDictionaryDechunker to put chunks back together
Return structured TaggedWord from IPosTagger

Instead of returning a string with a special format
ex: It/PRP 's/VBZ great/JJ --> collection of tagged words
Replaced ArrayList of objects by List<string> in OpenNlp interfaces

--> avoid casting in implementations of those
interfaces
Clean up Pair.cs (use Tuple instead)
Cleanup of code to stick to msdn recomendations
Return structured SentenceChunk from IChunker