Move jacobian calculation to DF

This PR moves the simple jacobian matrix definition from TrackingTools to DataFormats.
With this change we can properly compute the uncertainty on sum of Candidates as needed by btag for VertexCompositePtrCandidate.
(The fix for VertexCompositePtrCandidate wrt original Dinko's implementation will be in a separate later PR)

@ferencek @VinInn 
OK, but maybe at least TrackingJacobians.h or something like that. plain "jacobians.h" is too generic in this context.