Man(8) page for gluster-swift-gen-builder

Man page provides details on gluster-swift-gen-builder
script and its usage. Man page will be placed in section
8.

Bug: 1001033

https://bugzilla.redhat.com/show_bug.cgi?id=1001033

Change-Id: Ie172173d3873256facb55eb3be0accebe360025e
Signed-off-by: Chetan Risbud <crisbud@redhat.com>
Reviewed-on: http://review.gluster.org/6294
Reviewed-by: pushpesh sharma <psharma@redhat.com>
Tested-by: pushpesh sharma <psharma@redhat.com>
Reviewed-by: Luis Pabon <lpabon@redhat.com>
Tested-by: Luis Pabon <lpabon@redhat.com>