Revert "Stack.Package: keep as Sets rather than converting to/from lists (#32,#105)"
Revert "Stack.Package: keep as Sets rather than converting to/from lists (#32,#105)"

This reverts commit 650a12c43e59e5491e0794938ceaf88b287ead42.

juhp/stack,robstewart57/stack,martin-kolinek/stack,luigy/stack,MaxGabriel/stack,sinelaw/stack,MaxGabriel/stack,anton-dessiatov/stack,sjakobi/stack,supermario/stack,Fuuzetsu/stack,harendra-kumar/stack,narrative/stack,AndreasPK/stack,martin-kolinek/stack,AndreasPK/stack,akhileshs/stack,athanclark/stack,rrnewton/stack,anton-dessiatov/stack,mathhun/stack,ant1441/stack,kairuku/stack,Heather/stack,DanielG/stack,adinapoli/stack,joozek78/stack,Blaisorblade/stack,lukexi/stack,duplode/stack,keent/stack,duplode/stack,athanclark/stack,Heather/stack,lukexi/stack,robstewart57/stack,Andrew-the-Ubergeek/stack,markus1189/stack,vigoo/stack,rrnewton/stack,markus1189/stack,mathhun/stack,tedkornish/stack,bixuanzju/stack,cabrera/stack,harendra-kumar/stack,joozek78/stack,bixuanzju/stack,sinelaw/stack,rekka/stack,rubik/stack,narrative/stack,achernyak/stack,achernyak/stack,mrkkrp/stack,phadej/stack,wolftune/stack,deech/stack,meiersi-11ce/stack,bollu/stack,rvion/stack,Blaisorblade/stack,rvion/stack,phadej/stack,Fuuzetsu/stack,bollu/stack,rekka/stack,akhileshs/stack,MichielDerhaeg/stack,tedkornish/stack,Denommus/stack,juhp/stack,sjakobi/stack,keent/stack,supermario/stack,rubik/stack,AndrewRademacher/stack,chadbrewbaker/stack,kairuku/stack,AndrewRademacher/stack,agrafix/stack,wolftune/stack,agrafix/stack,fizruk/stack,DanielG/stack,deech/stack,meiersi-11ce/stack,Denommus/stack,cabrera/stack,adinapoli/stack,Andrew-the-Ubergeek/stack,chadbrewbaker/stack,vigoo/stack,ant1441/stack,fizruk/stack,luigy/stack,MichielDerhaeg/stack,mrkkrp/stack