TEST: Full Legacy Migration Workflow

This tests the full legacy migration workflow as it is anticipated for the big LHC repositories on a small guinea pig. It contains some snapshots of a small (20MB) 2.0 repository and gradually transforms it into a 2.1.x repository. Furthermore the test simulates both the stratum 1 replication and life client updates over the version boundary.
The test repository is imported in-place, meaning that both the data backend as well as the repository's keychain is in the right location before the actual import is started. This reflects the situation on the LHC production release manager machines.