Added ability to quickly remove an additional field

git-svn-id: https://plugins.svn.wordpress.org/simple-links/branches/searchable@927785 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updated LinkSetup test to match new structure

git-svn-id: https://plugins.svn.wordpress.org/simple-links/branches/searchable@927786 b8457f37-d9ea-0310-8a92-e5e31aec5664