Added tasks to stage RC dists

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/project-release-tools/trunk@1504953 13f79535-47bb-0310-9956-ffa450edef68
Improved SVN get, update and status tasks

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/project-release-tools/trunk@1505126 13f79535-47bb-0310-9956-ffa450edef68