Added option to use vertex0 when computing neutral candidates directions for isolation computation.

Option is on by default.
Using packedCandidate vertex makes inner veto ineffective.
Seems to be related to neutral packed candidates with displaced vertexes, most likely from conversions.
fixes to diphotonMVA producer on mass resolution wrt to correct vertex

some small corre
ctions to photon position used

correct photon 4 momentum
correct gamma 4 momentum
Few fixes and additions, mostly targeted to FWLite compatibility.

Changes to flashgg::Photon:
- Modified charged iso accessor to work with FWLite.
- Also added trailing _ to all data mebers.
- Recover shadowed reco::Photon isolation methods.

Imported parallel python module for job workflow control.
Merge pull request #106 from molmedon/correct_photon_4p

Correct photon 4p
Merge pull request #107 from musella/topic_fwlite_debug_rebase

Few fixes and additions, mostly targeted to FWLite compatibility.
Merge pull request #105 from musella/topic_neutrals_iso_direction

Use vertex0 when computing neutral candidates directions for isolation computation.