app.nlp.lexicon.WordLexicon: Increase efficiency and fix initialization bug.
ChainLink: New methods getNext and getPrev return Options.
More efficient MaximizeDiscrete.
Domain: further cleaning.
New classes DiscreteProposalSampler and DiscreteProposalMaximizer, more efficient than previous alternatives for iid DiscreteVars.
SegmentEvaluation: Better ensure efficiency by insisting on IndexedSeq, not just Seq.
DocumentAnnotator: Add further default DocumentAnnotators to DocumentAnnotatorMap.
lexicon.StopWords: inherit from WordLexicon not PhraseLexicon, for efficienty.
Remove SamplerSuite.  Not used.
Further work on NER, including adding history features to NER2.  IteratedConditionalModes no longer takes a type parameter.  New OntonotesNerDomain and Label.
Merge.
util.coref: Added code for weighted bipartite matching, and use it for CEAF-E and CEAF-M coref metrics
merge
added a method to ParseTree to get the subtree from a given token
util.coref: adding blanc
merge
New trait MutableLexicon.  New Method Lexicon.contains(TokenSpan).
New trait app.nlp.Load and LoadConll2003 and LoadPlainText now inherit from it.  Others should follow.  Note that Load (and now LoadPlainText) returns a Seq[Document].  Arguents modifying the load process are given to the Load subclass, not to the fromFile() method.
Merge.
util.coref: Debugging the AssignmentSolver