on keydown Enter (13) evaluate the ng-click statement of the primary button

I was facing a situation where I wanted the main button to be pressed when the Enter key was pressed. I added an option to make sure the ngDialog evaluates the `ng-click` contents of the button with the `.ngdialog-submit`. There is most likely another sexier way of doing this but thought I would raise the issue proactively ;)
@devcollectief angular's built-in jqLite doesn't support selectors, that won't work in pure angular app..