Veelken/veelken 7 0 x boosted taus

added jet substructure tools for seeding boosted tau reconstruction
(forward-port from 5_3_X)

includes improvements and minor bug-fixes
    - added protection that subjet has no constituents to VirtualJetProducer.cc
    - run CMSBoostedTauSeedingAlgorithm regardless of pruning/filtering being used in addition
    - added protection against pathological cases to BoostedTauSeedsProducer.cc
    - minor bug-fix: added missing initialization of useCMSBoostedTauSeedingAlgorithm_ flag
    (forward-port of commits
       https://github.com/veelken/cmssw/commit/985ac7ac45ac2b64021f0efb098c770b74247ed7
       https://github.com/veelken/cmssw/commit/6c99ae25a7cffe5f75e05d9a8d774171811540b7
     from CMSSW_5_3_X branch)
    - switch to getByToken and consumes interface
    - updated include guard and removed cvs specific labels from CMSBoostedTauSeedingAlgorithm.h