added "value" attribute to radio_items to better support arbitrary data selection

indra/llui/llradiogroup.cpp

indra/llui/llradiogroup.h

indra/llui/lluictrlfactory.cpp

indra/llui/lluictrlfactory.h

indra/llui/llview.cpp

indra/newview/llfloatertools.h

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

...a/newview/skins/default/xui/en/floater_settings_debug.xml

...a/newview/skins/default/xui/en/panel_preferences_chat.xml

...ewview/skins/default/xui/en/panel_preferences_general.xml

...view/skins/default/xui/en/panel_preferences_graphics1.xml

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