Mini aod part3 (72X)

Rebase of #3875. Since all the signatures already arrived in 71X I'll simply merge this in 72X. Original message.

> Based on top of CMSSW_7_1_X_2014-05-08-0200 (but mergeable, at least as of now)
>
>Include the relinking of e/gamma objects, more event content updates, functional cmsDriver integration.
>
>Tested workflows:

>```
cmsDriver.py miniAOD_data-prod -s PAT -n 100 --data --filein /store/relval/CMSSW_7_1_0_pre6/JetHT/RECO/PRE_R_71_V2_RelVal_jet2012C-v1/00000/2CBD40F5-E2C7-E311-8206-003048678AC0.root --eventcontent MINIAOD --runUnscheduled --conditions GR_R_70_V1::All --no_exec
cmsDriver.py miniAOD-prod -s PAT -n 100 --mc --filein /store/relval/CMSSW_7_1_0_pre6/RelValTTbar_13/GEN-SIM-RECO/PRE_LS171_V5-v1/00000/064AD022-51C7-E311-9714-003048679228.root --eventcontent MINIAODSIM --runUnscheduled --conditions auto:startup --no_exec
cmsDriver.py miniAOD-fsim-prod -s PAT -n 100 --mc --fast --filein /store/relval/CMSSW_7_1_0_pre7/RelValTTbar_13_AVE20/GEN-SIM-DIGI-RECO/PU_PRE_LS171_V7_FastSim-v1/00000/02658C92-B3D1-E311-98DB-02163E00CAA0.root --eventcontent MINIAODSIM --runUnscheduled --conditions PRE_LS171_V7::All --no_exec
>```

@arizzi @bendavid @gpetruc