Move the template shortcode functions to its own class.
Remove the template shortcode functions from cnShortcode.

Move the shortcode view controller to cnShortcode.
Remove dead/duplicate code from inc.shortcode.php.
Fix the character index so it'll repeat per user settings.

Remove cn_list_index legacy filters.
Rename cn_action_character_index and cn_action_return_to_target to
cn_list_character_index and cn_list_return_to_target respectively.
Update cn_action_return_to_target name to be cn_list_return_to_target.