Add option to display QuickShare only on single-view pages, hiding from blog index, archive, author, and taxonomy pages.

git-svn-id: https://plugins.svn.wordpress.org/quickshare/trunk@863414 b8457f37-d9ea-0310-8a92-e5e31aec5664
Add new `quickshare_show_output` filter, allowing extra control over where QuickShare should be displayed.

git-svn-id: https://plugins.svn.wordpress.org/quickshare/trunk@863468 b8457f37-d9ea-0310-8a92-e5e31aec5664