Merging construct_bfs#42

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dagalindo wants to merge 3 commits intobdsullivan:testingfrom

dagalindo:master

Commits on Nov 13, 2013

readding TDTree changes, plus updates to bfs tree construction
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Commits on Nov 18, 2013

implementation of Dourisboure & Gavoille's bfs algorithm, with up to 2 separator steps one of which uses METIS
dagalindo
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merging in upstream branch
dagalindo
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