Remove superfluous JUnit fixture files

All necessary JUnit files are created in the JUnit Features.
Remove legacy_features folder

All features have been moved, so the support files are not needed anymore.
Remove unneeded legacy_features Rake task
Merge pull request #557 from jimvm/remove_legacy_features

Remove legacy features
Merge pull request #556 from jimvm/remove_junit_fixtures

Remove superfluous JUnit fixture files