Add an #id option to buttons to jump to a div containing form

Problem/Motivation

If you have a multistep contact form placed in the footer region of your page, the page jumps to the top when you click Next /OR Back.
This cause the user to scroll down to the footer region to see the next step.

Steps to reproduce

Create a multistep form and place in in a footer region

Proposed resolution

Add an option to specify a #id to be added to the current page url on button submit.

E.g: If your current page is node/1 and your multistep form is in the #footer
Then the url for next will look like this: node/1#footer

User interface changes

Add a field to specify div #id to jump to when you submit next/back