packaging: fixed issue #178

- properly install init-scripts for Debian-based distros (based on files by user phoborg)
-> also added postrm and prerm scripts which stop and unregister the services (based on files by user phoborg)

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@2056 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534