#604976: Prevent Page Manager from throwing errors when no modules that provide variants are available.

#573646: Attempt to make sure page manager does not try to respond to menu/theme hooks when CTools is not enabled.

#665338 by andypost: Fix instances of ctools_context_handler_render that used wrong format for sending arguments.

#657474: Deleting a custom task designated as the site home page no longer deletes the site_frontpage variable.

Deleting the site_frontpage variable alongside the custom task that had previously owned it worked OK for tasks in the database, but made for an confusing, non-transparent extra step when tasks were exported to code. The deletion logic is now entirely gone, for both actual deletions and reversions to code. Improved helptext on the relevant form widget also makes the process slightly more transparent.

Show a LOCK icon on the page list when pages are locked for editing either by the current user or another user.

#589342: Introduce page_manager_get_current_page() to get information about the current page manager page.

- php potx-cli.php --mode=multiple
- msgcat views_content-plugins-content_types.pot views_content-plugins-views.pot views_content.pot --use-first --no-wrap -o views_content.combined.pot
- msgcat page_manager-plugins-tasks.pot page_manager-theme.pot page_manager.pot --use-first --no-wrap -o page_manager.combined.pot
- msgcat ctools.pot includes.pot plugins-access.pot plugins-arguments.pot plugins-content_types-block.pot plugins-content_types-custom.pot plugins-content_types-form.pot plugins-content_types-node.pot plugins-content_types-node_context.pot plugins-content_types-node_form.pot plugins-content_types-term_context.pot plugins-content_types-user_context.pot plugins-content_types-vocabulary_context.pot plugins-contexts.pot plugins-relationships.pot --use-first --no-wrap -o ctools.combined.pot