Add validation and access checking to addressable content.

page_manager/page_manager.module

page_manager/plugins/tasks/blog.inc

page_manager/plugins/tasks/blog_user.inc

page_manager/plugins/tasks/contact_site.inc

page_manager/plugins/tasks/contact_user.inc

page_manager/plugins/tasks/node_edit.inc

page_manager/plugins/tasks/node_view.inc

page_manager/plugins/tasks/page.inc

page_manager/plugins/tasks/poll.inc

page_manager/plugins/tasks/search.inc

page_manager/plugins/tasks/term_view.inc

page_manager/plugins/tasks/user_edit.inc

page_manager/plugins/tasks/user_view.inc