TEST: Basic Infrastructure for Cloud Testing of the S3 Backend

This adds basic infrastructure needed for backend integration test cases based on S3. It allows to transparently run a FakeS3 on the same machine and use it for testing. Additionally it includes an experimental S3 test run in SLC6 x64.

For the moment the Stratum 1 tests should work, however the stratum 1 won't be hosted on S3. Instead they will host the stratum 0 on S3 and snapshot them to the local disk (which is actually also an interesting test case).