Add search all code

git-svn-id: https://plugins.svn.wordpress.org/string-locator/trunk@955274 b8457f37-d9ea-0310-8a92-e5e31aec5664
Move search function to the general plugin class for easy re-use

git-svn-id: https://plugins.svn.wordpress.org/string-locator/trunk@955275 b8457f37-d9ea-0310-8a92-e5e31aec5664