Fixed a few issues:
Issue #2155077 by SteffenR: Fix comment syntax in print.css
Issue #2155173 by SteffenR: Rewrite and remove no longer available theme hooks
Issue #2155161 by SteffenR: Fix broken styling for sidebar items.
Issue #2155143 by SteffenR: Fix broken main menu styling.
Issue #2155085 by SteffenR: Fix undefined index: href in busy_menu_local_task()
Issue #2028627 by lucastockmann: outsource conditional comments to busy.theme.