Change also luxset with vp-nextfitruncard

[niclaurenti]

This PR's aim is to change the also luxset (if present) with vp-nextfitruncard, and set it to the input fit.

In this case there's no need to change also the luxseed since it is used only by the last iteration of the fit, i.e. when additional_errors is set to True (operation that has to be done manually since one in principle could do as many iterations as he wishes)

[RoyStegeman]

What about the seed? Oops should have read, sorry!

[niclaurenti]

What about the seed?

In this case there is no need to change it since it will never be used until the last iteration of the fit. So even if all the runcards of the iterated fits will have the same luxseed it will be actually used only in the last one (the une in which the additional errors are enabled).
But if you want for me it's perfectly fine to change also the seed

[RoyStegeman]

You're right - the seed is not something that's included in the loss function of previous iterations so it doesn't need to change.