Switch from template-based return types to dynamic typing, and use...

Switch from template-based return types to dynamic typing, and use boost::function for callback. This reduces code complexity a bit and should help compile times.

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@3405 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534