Add listing syntax. (moves plugin components..)

listing syntax:
~~TODOLIST~~
~~TODOLIST completed:yes~~
~~TODOLIST completed:no assigned:no~~
~~TODOLIST assigned:yes~~
~~TODOLIST assigned:@User,@work~~
~~TODOLIST assigned:User,work~~

==searchpattern==
The searchpattern listing is broken by moving syntax.php to
syntax/todo.php. It can be fixed by let searchpattern allow _ of the
'todo_todo' and removing the plugin_is_disabled checks. These last
checks require as input the plugin name 'todo' instead of plugin
component name 'todo_todo'
cleanup PHPDocs, give some methods protected visibility
minor issues
Merge pull request #10 from Klap-in/master

Added new listing syntax