more verbose migration history
FIX: parameter passing + CREATOR_VERSION discovery
move CVMFS_UNION_FS_TYPE addition to correct migration step
reload (updated) repo info after migration
clearify check_repository_compatibility()
update migrate()
enable catalog migration from 2.1.7 to 2.1.15
update catalog schema version to 2.5
FIX: $destination_version did not expand
check if change is necessary before applying it
might be useful when migrate needs to run more than once (i.e. when errors occured)
FIX: typo
hardcode version strings
remount after repo migration to 2.1.15
verbose error messages
refactor version comparison
FIX: repo_is_incompatible() taking stuff out of the global namespace
use version_equal() instead of direct comparison
prevent manipulation of repositories by older cvmfs versions
Merge pull request #257 from reneme/no_backward_compatibility

Prevent manipulation of repositories by legacy CVMFS versions
improve logging on cache cleanup errors