[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.
I am inclined to think we should effect the change through one or the other (resource config update or resource operation) but not both for a couple reasons. I think doing both might make debugging more difficult, and I think it makes the code more complex than it otherwise might need to be. We want users to make changes through the admin UI or through the CLI (using the remote API). In both cases the user has a single interface for making the change; so, I don't know that we need to or should expose the functionality in two places at the plugin level.