Drop CA8 jets from RECO/AOD and switch to AK8 jets for jet substucture

This is a long outstanding issue to switch from CA8 to AK8 for jet substructure algorithms.
It would have resulted in merge conflicts with #6542 which went in only this weekend.
Though this is after the 730_pre3 deadline, we would very much like to switch this as CA8 jets are obsolete for analyses and in fact one can remove one jet algorithm in RECO by this change.
Here are the changes:
- drop ca8 collection from RECO/AOD, since ak8 jets are recommended instead
- switch from ca8 to ak8 for substructure algorithms in RECO/AOD
- update PAT and DQM accordingly
- update default parameters for N-subjettiness and softdrop (these are not run in RECO)
Automatically ported from CMSSW_7_3_X #6588