Python interface: leak bugfix, many new methods
python/bllipparser/RerankingParser.py:
    Tree:
        Acquire SWIG pointers if given an InputTree.
            This fixes a serious memory leak.
        Add __getitem__, all_subtrees, is_preterminal methods
        Convert label method to property
            (via DeprecatedGetter so it will still work as a method
            for now but spit out a warning)
        Add token, labelSuffix properties
        Add trees_from_string, trees_from_file classmethods
    Sentence:
        Can now be constructed directly from a SentRep (in which case
            we acquire the SWIG pointer)
        Add __repr__ method
        Add sentences_from_string, sentences_from_file classmethods

first-stage/PARSE/swig/wrapper.i:
    Add {inputTrees,sentReps}From{String,File} methods
    Add several setters to InputTree class
    Minor comments, %template cleanups

first-stage/PARSE/InputTree.h:
    Allow words of InputTrees to be set

python/bllipparser/__init__.py:
    Allow Sentence to be imported