MRC:

* Added support for replica update policies in X-Loc lists. Setting the read-only attribute of a file will automatically set the file's replica update policy in the X-Loc list to 'read only replication'; removing the attribute will set it back to 'none'.
* added error message that occurs when a wrong version of the database file is attempted to be loaded by the MRC

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@359 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534