adapt widgets and text rendering to new font rendering

no background for text rendering anymore

frontend/ui/widget/scrolltextwidget.lua

@@ -15,7 +15,6 @@ Text widget with vertical scroll bar
 local ScrollTextWidget = InputContainer:new{
     text = nil,
     face = nil,
-    bgcolor = 0.0, -- [0.0, 1.0]
     fgcolor = 1.0, -- [0.0, 1.0]
     width = 400,
     height = 20,
@@ -28,7 +27,6 @@ function ScrollTextWidget:init()
     self.text_widget = TextBoxWidget:new{
         text = self.text,
         face = self.face,
-        bgcolor = self.bgcolor,
         fgcolor = self.fgcolor,
         width = self.width - self.scroll_bar_width - self.text_scroll_span,
         height = self.height