Moved the implementation of the JetCorrector so that the needed
class can be obtained from the Event rather than the EventSetup.
This is needed since
1) having an EventSetup class access data from the Event is against
 CMSSW rules
2) it is not possible to make the needed 'consumes' call with the
 previous design.
The new implementation lives in the namespace reco while the old
implementation is still in the global namespace until the old
can be removed.

The ChainedJetCorrectorProducer is the equivalent to the previous
JetCorrectionESChain but for the Event based reco::JetCorrector.