Cvm 617

Removes CERN specific configuration from cvmfs package.  The configuration and public keys are provided in cvmfs-config-... packages.  The cvmfs-config-cern package replaces cvmfs-keys and cvmfs-init-scripts.
Regarding CVMFS_CONFIG_REPOSITORY, I'm not sure yet.  I see your point but it would give us more flexibility to have a config repository at Cern.