Scalyr agent sidecar for log shipping (#190)

* Scalyr agent sidecar for log shipping

* Remove the default for the Scalyr image

Now the image needs to be specified explicitly to enable log shipping to
Scalyr.  This removes the problem of having to generate the config file
or publish our agent image repository.

* Add configuration variable for Scalyr server URL

Defaults to the EU address.

* Alter style

Newlines are cheap and make code easier to edit/refactor, but ok.

* Fix StatefulSet comparison logic

I broke it when I made the comparison consider all containers in the
PostgreSQL pod.