Add filter to allow other plugins to interact with out metaboxes outside of the standard pages
Renamed the filter and added API documentation
Merge branch 'master' of git://github.com/Yoast/wordpress-seo into Issue-1242-metabox-loading
Merge pull request #1275 from jrfnl/Issue-1242-metabox-loading

Add filter to allow other plugins to interact with our metaboxes outside...