=act #16330 deprecating akka.util.Crypt

 * Fix for #16330 
 * Additionally clean several files up: final modifiers on objects and final class members, unused imports, iterators.nonEmpty instead of !iterators.isEmpty
non empty is an implicit where as isEmpty is a direct call, not sure if it's via an value class, but I'd rather avoid the chance it might (cause some perf overhead), since this seems to be a rather low-level class.