DEV-50015 FIX Implement changes to the Buy L$ button in the top bar of the viewer

indra/newview/llfloateruipreview.cpp

indra/newview/skins/default/textures/textures.xml

...wview/skins/default/textures/widgets/bevel_background.png

indra/newview/skins/default/textures/widgets/buy_off.png

indra/newview/skins/default/textures/widgets/buy_over.png

indra/newview/skins/default/textures/widgets/buy_press.png

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