doc: Drop volfiles from documentation tree

They're mostly useless.

Change-Id: Ib5db6f4439fee16e461afc0b0cd3b71c717a19c6
Signed-off-by: Lubomir Rintel <lubo.rintel@gooddata.com>
Reviewed-on: http://review.gluster.org/5475
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Vijay Bellur <vbellur@redhat.com>