Add PostgreSQL option for Ceilometer backend

Adds the PostgreSQL case for a Ceilometer backend and
initializes Ceilometer accordingly.

Closes-Bug: #1244381
Change-Id: Iefc5bb7eea6e9efa1f2ad04f1f8dc714e3404c9c
Enables Swift crossdomain middleware by default

This step is needed to enable its testing in Tempest. The patch adds a
variable SWIFT_EXTRAS_MIDDLEWARE_NO_AUTH that holds a list of
middlewares inserted in the pipeline before authentication middlewares
(tempauth, keystoneauth, ...).

Change-Id: I1927103feff997a354ccf82ccf12aa77db083ad3
Merge "Enables Swift crossdomain middleware by default"
Merge "Add PostgreSQL option for Ceilometer backend"