cluster/cassis: Cast promoters to upper
cluster/cassis: Cast promoters to upper

Cast promoter sequences to upper case letters while checking if the
sequence contains at least one 'A', 'C', 'G', or 'T'. This makes the
check robust against (mixed) upper/lower case promoter sequences.

L--U--P--U--S/skeleton,L--U--P--U--S/skeleton