Doh, critical bug in recent bucket changes
Show an alert while migrating
Logging
Fix bogus "MIME type is null" warnings
Keep the MIME type from the error message if possible
Keep the MIME type from the error
Keep the MIME type even if we fail because we don't like it
Always delete node.db4o* after migrating, even if it fails.
Don't imply client.dat is small.
Wait for the actual write to finish before we delete node.db4o*