def extract
      return config.instance_dir if extracted?

      jar_file = download

      FileUtils.mkdir_p config.instance_dir
      FileUtils.cp jar_file, config.binary_path
      self.extracted_version = config.version

      config.instance_dir
    end
def extract
      return config.instance_dir if extracted?

      jar_file = download

      FileUtils.mkdir_p config.instance_dir
      FileUtils.cp jar_file, config.binary_path
      self.extracted_version = config.version

      config.instance_dir
    end
extract a copy of fcrepo to instance_dir
 Does noting if fcrepo already exists at instance_dir
 @return [String] instance_dir Directory where fcrepo has been installed