Small updates to multi reader

[lukaspie]

This solves two problems:

1. If, in your config file, you have a list with a wildcard like this "peakPEAK[peak*]/data/@xes":["@attrs:component*/kx, @attrs:component*/ky"], all of these values in the list gets replace as for non-list cases.
2. If you have multiple options to resolve a wildcard value like
   "peakPEAK[peak*]/intensity":"['@attrs:component*/data_cps', '@attrs:component*/data']", where the reader first tries to fill from the path component*/data_cps and then from @attrs:component*/data', there was an issue with the dict iterator before if the first attempt at filling does not work. This is fixed here.

[RonHildebrandt]

I get the first part.
The second, with the .copy is most probably necessary, as here during iteration some changes were made? Anyway, I think its always saver todo it like this.

Therefore: lgtm

[lukaspie]

The second, with the .copy is most probably necessary, as here during iteration some changes were made? Anyway, I think its always saver todo it like this.

Exactly, that was the problem. Thanks for the review.