Move component_manager to a separated object. - component_manager is a mixin for domview. - domview inherit component_manager to mixing-in component_manager. - There is no boundary between component_manager and domview, hard to be managed and reused. - component_manager is a separated object that hold a reference to corresponding domview. - domview delegate attribute accessing to component_manager object to expose attributes and methods of component_manager. (__getattr__()) - component_manager is still a mix-in of domview.

<inkscape-extension>
    <name>Convert to Symbol</name>
    <id>MadButterfly.ConvertSymbol</id>
	<dependency type="executable" location="extensions">AssignSymbol.py</dependency>
	<dependency type="executable" location="extensions">inkex.py</dependency>
    <effect>
		<object-type>group</object-type>
		<effects-menu>
			<submenu _name="MadButterfly"/>
		</effects-menu>
    </effect>
    <script>
        <command reldir="extensions" interpreter="python">AssignSymbol.py</command>
    </script>
</inkscape-extension>