Main plugin file name matches plugin name for consistency

git-svn-id: https://plugins.svn.wordpress.org/share-on-xing/trunk@993119 b8457f37-d9ea-0310-8a92-e5e31aec5664
v1.0.5: Link to settings page is back

git-svn-id: https://plugins.svn.wordpress.org/share-on-xing/trunk@993120 b8457f37-d9ea-0310-8a92-e5e31aec5664