Bootstrap/update

Support both bootstrap and update operations:
- `bootstrap()` method now takes in a parameter that specifies the `call` web service name, just like the other methods. This allows it to access both the bootstrap and update web services.
- Rename the sample IN file from `02-data.zip` to `02-bootstrap.zip`, and OUT file from `02-data.txt` to `02-bootstrap.zip`, to match this change.

With this change, files like `testcases/in/04-update.zip` and `testcases/out/04-update.zip` will be handled properly.

Ignore directories in `testcases/in/`:
- Swap out `FilenameFilter` for `FileFilter`, and add condition to ignore entries that are directories