Support Oracle JDBC Adapter

I tried using database_cleaner on a Rails project using the ActiveRecord JDBC Adapter on an Oracle database. The first issue I came across was the following error message when trying to truncate:

```
NameError: uninitialized constant DatabaseCleaner::ActiveRecord::StatementInvalid
```

I traced this an improperly scoped class reference at `lib/database_cleaner/active_record/truncation.rb:117`.

Then I received `ORA-00911: invalid character` errors when trying to truncate. Oracle does not support semi-colons in TRUNCATE TABLE statements. So we need to use the same syntax with a JdbcOracleConnection as used by the OracleEnhancedAdapter.