adjust length of usename field in creation of db-user
A MySQL username can only be 16 characters, no problem in general, but because of the prefix (clientname by default), a large part of those 16 characters are already used. When I create a new user, the form accepts more characters then I can really use, and it just ignores everything over 16 characters. I think it would be good to make sure that the client cannot type a name that's too long.