Add FTPS option for KeyManager (and TrustManager) to support FTPS servers that ask for the client certificate for authentication (VFS-468).

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/vfs@1450863 13f79535-47bb-0310-9956-ffa450edef68
Update changes.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/vfs@1450868 13f79535-47bb-0310-9956-ffa450edef68