Any field with multiple values (grid, select, date, time) does not create proper mail tokens

If any field that requires multiple values (grid, select, date, time) is added to the form and an e-mail is configured, several notices are thrown:

# notice: Array to string conversion in /Users/nate/Sites/drupal6/sites/all/modules/webform/webform.module on line 1993.

This is caused by the _webform_filter_values() function taking a $submission parameter, then it trying to create %cid[cid] and %value[name] tokens. Sometimes the value is not a string be an array. We'll need to convert these into strings (perhaps through the existing theme_webform_mail_*() functions) so that they can be used in tokens. It will also increase the consistency in the e-mails if the same rendering is used in both places.