Widgets: drop onto closed sidebars.
- Make dropping a widget easier by preventing the source sidebar from resizing while the widget is being dragged.
- Move widgets dropped on closed sidebars to the top. UI Sortable places them randomly near the bottom.
- Fix possible regression in wp_list_widget_controls(), add an optional argument to output the sidebar name inside the sortable container.
- Updated styles for sidebar description and widget-hover class.
Part props shaunandrews, fixes #25952.
Built from https://develop.svn.wordpress.org/trunk@26426


git-svn-id: http://core.svn.wordpress.org/trunk@26326 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Widgets: remove leftover debug bits and fix jshint warnings in widgets.js, see #25952.
Built from https://develop.svn.wordpress.org/trunk@26427


git-svn-id: http://core.svn.wordpress.org/trunk@26327 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Heartbeat: introduce "suspend" functionality and enable it after 20 min. of inactivity, see #25073.
Built from https://develop.svn.wordpress.org/trunk@26428


git-svn-id: http://core.svn.wordpress.org/trunk@26328 1a063a9b-81f0-0310-95a4-ce76da25c4cd