Get all SuSE packages from repo if necessary

For older OpenSuSE versions (12.1 comes to mind), the packages mentioned
here are only available in the repository and not the base distro, so we
should start out by adding it instead of doing it later in the process.
Recommend ERT also on Debian

Using ERT will give a more full-featured toolkit, and we already
recommend adding the PPA repository.
Provide instructions for installing ERT on SuSE

We just reuse the RedHat-repo containing precompiled libraries.
Merge pull request #255 from rolk/255_repo

Use science repo on SuSE, recommend ERT on Debian