implement 1.9.17 new api - getTestSuiteAttachments

[lczub]

TL future release 1.9.17 delivers new api getTestSuiteAttachments

related TL pull request TestLinkOpenSourceTRMS/testlink-code#84

• added API function to retrieve a testsuite's attachments

  /**
   * Gets attachments for specified test suite.
   * The attachment file content is Base64 encoded. To save the file to disk in client,
   * Base64 decode the content and write file in binary mode.
   *
   * @param struct $args
   * @param string $args["devKey"] Developer key
   * @param int $args["testsuiteid"]: id of the testsuite
   *
   * @return mixed $resultInfo
   * @author dennis@etern-it.de
   */
  public function getTestSuiteAttachments($args)