new page manager task handler plugin for tasks to render simple ctools content. use page_manager_get_current_page() to grab context for bricks on pages with task handlers.

Use page manager tasks to determine context. Tasks must be enabled, but no task
handler is needed as long as the tasks call hook_page_manager_override().

Boxes do not take arguments. They can have required contexts. The task's
argument contexts are passed into the boxes' base contexts.