MAINT-5297 Allow global toggle of 'View People Icons' - Global switch part

indra/newview/app_settings/settings.xml

indra/newview/llavatarlist.cpp

indra/newview/llavatarlist.h

indra/newview/llconversationview.cpp

indra/newview/llfloaterimcontainer.cpp

indra/newview/llpanelpeople.cpp

...newview/skins/default/xui/en/menu_people_friends_view.xml

.../newview/skins/default/xui/en/menu_people_nearby_view.xml

.../newview/skins/default/xui/en/menu_people_recent_view.xml

.../newview/skins/default/xui/en/panel_preferences_setup.xml