submitted patch 10290 - add reset_tag helper method.

I found myself wishing I could create a form reset button as easily as I can a submit button. So, now I can.

If you apply this patch, you can too!

If you have any forms with reset buttons, please try out this patch and comment on the ticket.

This is my first rails patch, so if I've goofed at all, please (gently) let me know.