Add user timezone to messages

Messages provided with commerce_dunning_defaults use format_date without any consideration for the user's timezone.

If user timezones are being used, leads to messages being sent that state the next time a charge will occur, but the time is relative to the site.

There should be logic that checks if a user timezone exists, and if so, use the information to set !charge-attempt-date. Otherwise, use the site's timezone.

See the attached patch, thanks.