Minor: Get rid of a bunch of superfluous "&$this" lines. This isn't PHP 4, we don't need to explicitly pass objects by reference.

git-svn-id: https://plugins.svn.wordpress.org/broken-link-checker/trunk@1024963 b8457f37-d9ea-0310-8a92-e5e31aec5664
Remove screen_icon from the settings page. WP deprecated screen icons a while ago.

git-svn-id: https://plugins.svn.wordpress.org/broken-link-checker/trunk@1024964 b8457f37-d9ea-0310-8a92-e5e31aec5664