ticket:9101: fix RuleBasedCollator::getCollationKey(empty string): write empty levels, not an empty key

git-svn-id: http://source.icu-project.org/repos/icu/icu@34611 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10483: update readme for ver no

git-svn-id: http://source.icu-project.org/repos/icu/icu@34612 251d0590-4201-4cf1-90de-194747b24ca1
ticket:9101: some more bug fixes; intltest passes now

git-svn-id: http://source.icu-project.org/repos/icu/icu@34613 251d0590-4201-4cf1-90de-194747b24ca1