Simple UI: User Login form redirect/destination refactor

The Simple UI module does a form alter on the login form and forces a ?destination to the $form['#action] (hardcoded). This will redirect the user to the dashboard, or w/e page you have in site information for the default front page.

The problem stems from when I want to send someone to the login page and provide a "destination=[url]" to the URL so once logged in, they return back to the URL they came from. If I provide a destination to the login link and then fill out the login form with an error, the page will refresh and the new url will have two destinations on it.

myurl.com/user/login?destination=[original]?destination=dashboard

I have attached a patch that will redirect the user to the dashboard, while at the same time respecting the destination parameter. It should give it the most flexibility.