OSD-replication:

- fixed some bugs
- much more monitoring in OSD
- second RPC-client on OSD only used by replication
- TransferStrategies refactored
- new TransferStrategies (RarestFirst, SequentialPrefetching)
- ObjectSets will be used by TransferStrategies now
- changed semantic of OSD-selection in SequentialStrategy
- more tests
- ObjectSet clonable now

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@1240 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534