adds support for nfs storage pools

we use nfs here, so i added support for nfs [netfs] storage pools.  small disclaimer: i've not specifically tested glusterfs or cifs - only nfs.

![screen shot 2014-10-04 at 20 54 59](https://cloud.githubusercontent.com/assets/7424193/4517314/677cd9a4-4c2a-11e4-9ee8-e6ac5ae7090d.png)