Drop CA8 jets from RECO/AOD, switch to AK8 jets for jet substucture, add softdrop - rebase

Rebase of #6621

This is a long outstanding issue to switch from CA8 to AK8 for jet substructure algorithms.
CA8 jets are obsolete for analyses and in fact one can remove one jet algorithm in RECO by this change.
Also pruning is recommended to be replaced by softdrop for the next Run, therefore add it to RECO.
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
    add softdrop to RECO/AOD
    update DQM accordingly
    update default parameters for N-subjettiness and softdrop (these are not run in RECO)
    fix softdrop jet producer



The documentation for AK8 based jet substructure and softdrop is in
http://cms.cern.ch/iCMS/analysisadmin/cadi?ancode=JME-14-002
It is an update on the document based on CA8 jets and pruning:
http://cms.cern.ch/iCMS/analysisadmin/cadi?ancode=JME-13-006

Validation of Softdrop performance against Pruning was shown in this talk:
https://indico.cern.ch/event/336245/contribution/4
Remove, since already in the line above.