Add plotter to retrieve normalization effect of theory systematics at ttB level

I figure it was easier to do it just once in a separate plotter, than to squeeze this into the unfoldingPlotter.

This produces a YAML file that looks like this:

powheg_4FS:
    pdfDown: 0.9712332799989172
    pdfUp: 1.0287674551937036
    psFSRDown: 1.0012873802848208
    psFSRUp: 0.9990931462360679
    psISRDown: 1.0018730077617866
    psISRUp: 0.9985271701356928
    qcdMuFDown: 1.03460182342414
    qcdMuFUp: 0.9749808885020838
    qcdMuRDown: 1.3418727639495327
    qcdMuRFDown: 1.3417211362100763
    qcdMuRFUp: 0.6918932791716198
    qcdMuRUp: 0.721693279919291
    topPt: 0.9838305594458754
powheg_5FS:
    pdfDown: 0.9491977352020184
    pdfUp: 1.0507965242645174
    psFSRDown: 1.1519917536600055
    psFSRUp: 0.8984246972509904
    psISRDown: 1.0248103633581689
    psISRUp: 0.9806493662957967
    qcdMuFDown: 1.0290797453027525
    qcdMuFUp: 0.9766607859089645
    qcdMuRDown: 1.1257989795798686
    qcdMuRFDown: 1.1532766512659771
    qcdMuRFUp: 0.8655383354678515
    qcdMuRUp: 0.8897398944103276
    topPt: 0.9838065093955597

We'll now just need this in the unfolding code to add those as normalization uncertainties on ttB_OOA, while rescaling the shape variations to remove those normalization effects.