Dash cleanup.
 * Use wp_add_dashboard_widget() rather than add_meta_box().
 * Use original functions like wp_dashboard_primary(), wp_dashboard_right_now(), wp_dashboard_quick_press() (where possible).
 * Only include plugins section of the news widget when appropriate, which necessitates the set_current_screen() via the ajax action.
 * Remove some debug cruft that was preventing caching and invalidation.
 * Simplify lots of things where possible.
see #25824.

Built from https://develop.svn.wordpress.org/trunk@26220


git-svn-id: http://core.svn.wordpress.org/trunk@26128 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Merge wp_dashboard_recent_quickdrafts() into wp_dashboard_quick_press(). see #25824.

Built from https://develop.svn.wordpress.org/trunk@26221


git-svn-id: http://core.svn.wordpress.org/trunk@26129 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Make the Install Plugins search results page responsive, so the table doesn't overflow the viewport. Props joen, fixes #25976.


Built from https://develop.svn.wordpress.org/trunk@26223


git-svn-id: http://core.svn.wordpress.org/trunk@26130 1a063a9b-81f0-0310-95a4-ce76da25c4cd