Major JME developments for 73x

This PR contains a large number of JME developments for 73x : 

1. Updates to use new fastjet 3.1.0 (https://github.com/cms-externals/fastjet/pull/8)
2. Updates to new API for n-subjettiness for fastjet-contrib 1.014 (https://github.com/cms-externals/fastjet-contrib/pull/2)
3. Added changes to PUPPI from the code review here (https://github.com/cms-sw/cmssw/pull/5500)
4. Added several new tools, none of which are to be executed in RECO until further notice : 
   * Constituent subtraction
   * SoftKiller
   * SoftDrop
   * PUPPI

Two notes : 
 - There is a new package, CommonTools/PileupModules. It would aid development to have these separate from CommonTools/ParticleFlow (which is focused on the "top projection" code). 
 - The current output is set up as an intermediate stage where PFCandidates are produced along with a valueMap of four vectors. This is a stand-in until I make a migration to the ThinnedCollection, but this is better treated together rather than piecemeal. 


Also adding @violatingcp and @nhanvtran to watch this. 



Final note : This seems to be stuck "Checking mergeability...". I have updated to CMSSW_7_3_X_2014-11-07-0200 and it merges fine, so I presume this is a github issue.