SL-13479 Dedicated top-level menu for avatar editing

indra/newview/llviewermenu.cpp

indra/newview/skins/default/xui/en/floater_avatar.xml

indra/newview/skins/default/xui/en/floater_my_appearance.xml

indra/newview/skins/default/xui/en/floater_my_scripts.xml

indra/newview/skins/default/xui/en/menu_attachment_other.xml

indra/newview/skins/default/xui/en/menu_attachment_self.xml

indra/newview/skins/default/xui/en/menu_avatar_other.xml

indra/newview/skins/default/xui/en/menu_avatar_self.xml

indra/newview/skins/default/xui/en/menu_viewer.xml

indra/newview/skins/default/xui/en/panel_edit_wearable.xml

indra/newview/skins/default/xui/en/panel_outfit_edit.xml