pre-migration cleanup
cleanup cvmfs_server changes
FIX: create backend storage only if needed
add is_s3_upstream() to cvmfs_server
`cvmfs_server check` is S3 aware
show storage type in `cvmfs_server list`
add `cvmfs_server mkfs -s` to create S3 repos
`cvmfs_server add-replica -s` for S3 based Stratum1
remove S3 stratum1 support for now
FIX: integration test 514 for S3
allow for S3 repos in test_functions::create_repo()
FIX: check_catalog_presence() and get_catalog_count()
test adaption for stratum 1s1 on S3
rename get_repo_storage() to get_local_repo_storage()
adapt get_repo_url() to cope with S3 as well