[BZ 1074636] Add ability to move storage node datafiles

This patch would add the ability of moving commit_log, saved_caches and a single data directories to a new location. The process is time consuming and involves shutting down the storage node before doing the move and configuration update. If it's a single node deployment, this will turn the server to maintenance mode while doing the move. It also means that this patch will not able to restart the node, as agent will stop accepting the command (there's a separate discussion of that in rhq-devel, and solving that issue is required before this can be merged).

This change also provides the storage node with one new operation, "moveDataFiles" and changes the behaviour of updateConfiguration operation.
The ```retrieveConfiguration``` and ```updateConfiguration``` methods are getting pretty big and contain a lot of logic for mapping back and forth between the resource and plugin config object and the storage config composite. I would like to see that code refactored, pulled out into a separate class which also includes the logic for deciding whether or not we need to perform a resource config update. Doing so will make it much easier to write some unit tests, something that is lacking.