update diboson cross sections

[jabuschh]

see issue #254

Please don't merge yet, I'd like to wait for the final confirmation of these values from our GEN contact.

[anmalara]

I'm not convinced you should change the central value. But rather implement is a k factor correction.

[MatthiesC]

I'm not convinced you should change the central value. But rather implement is a k factor correction.

I second that

[jabuschh]

changed it ;)

[anmalara]

Thanks, @jabuschh. I'm not sure why the old k-factors were removed from here to here, but it's good that now they are back. Compared to the old ones, there is a ~2% change with the final xsec, so it's consistent with EOY numbers.

[jabuschh]

I also got the confirmation for these values from our GEN expert, so we're good to go, I guess.

[jabuschh]

Shall we merge this then? :)