FELIX-4467 Configure global extender capability

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1590350 13f79535-47bb-0310-9956-ffa450edef68
FELIX-4469 scrcommand help should not give NPE

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1590351 13f79535-47bb-0310-9956-ffa450edef68