Hooks in get_paths and create_open for reordering devices.

[Jonathan Steinert]

I see that I left the term 'FilePaths' in the 5th patch in this set 
where I shouldn't have, I'm already fixing that.

Jonathan Steinert wrote:
> I have another patchset here which refactors a little code and adds 
> two hooks for the ordering of devices for results to the create_open 
> and get_paths commands.
>
> The 5th patch in this set shows the goal I'm moving towards, a plugin 
> that prioritizes local storage nodes (defined by the network zones 
> provided by the MogileFS::Network module(1))
>
> Any comments on this design?
>
> --hachi
>
> (1) The MogileFS::Network module is originally from Andy McFarland on 
> this list October 3, 2007. Slightly modified now.