Use notification pools by default and use the same notification
topic as ceilometer, separate notification topic is no need to add.
Change-Id: Ieef1ece78e6e8d20abfeea9546e1a9170b7eeb70
As devstack plugin is added, this commit revises install doc about
installing bilean via devstack.
Change-Id: I6052e83a3d503b941e8fc44a0db9f1f0d73b5816