Rework search to filter instead of jumping to first one

[ptrcnull]

in case of artist names like firstArtist / secondArtist, you can't properly search for secondArtist as it just jumps to the first result; the search feature could instead filter the results

[spezifisch]

You can press Return to get out of the search input field, then press 'n' to jump to the next match.
I like the idea of filtering the list though. Currently the artist list is a tview.List. The search just calls FindItems which makes the code pretty easy from our side. Filtering would probably best be implemented as an extension or patch to tview's List.