introduce new log files for S3 tests
Refactor: common log file handling
add utility function to install ruby gems
add utility functions to handle FakeS3
integrate S3 test path in SLC6 x64
(temporarily) switch off stratum1 with S3
Merge pull request #473 from reneme/feature-s3_cloud_testing

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).