Fix various typos

Fixes various user-facing and non-user-facing typos

Found via: codespell -S "./po,*.appdata.xml,*.desktop,*.fits,*.kmt,*.mrc,*.pdf,*.po" -L als,buis,caf,carret,checkin,chello,childrens,childs,commun,compres,currentry,datas,dokument,egal,fo,hsi,leadin,ot,outin,pard,pixelx,slin,som,ue,tabe,tabl,te,wll