Align Modal "Add" button to the top-left of widgets

I've noticed that custom widgets and Views Content Panes in particular have an issue where the right-column stretches out so far that you can't click the "Add" button without hacking CSS on-the-fly to get it to show up. I've attached a patch that simply aligns the button to the top-left of widget divs instead of top-right, which is the quickest fix that I've found for this so-far.

The "best" solution would probably be to figure out how to set an appropriate max-width for that column that stops the off-screen overflow, but I have not figured that out yet. Enjoy!