added custom field support

git-svn-id: https://plugins.svn.wordpress.org/sb-child-list/trunk@784228 b8457f37-d9ea-0310-8a92-e5e31aec5664
added support for category filtering for pages. can be accomplished using category="slug or name" in the sb_child_list shortcode

git-svn-id: https://plugins.svn.wordpress.org/sb-child-list/trunk@784863 b8457f37-d9ea-0310-8a92-e5e31aec5664