Keyboard: better isolation of FR/ES/TR from EN base

dofile() wasn't enough to copy en_keyboard, as the references
to key popups would still be shared, and hacks to them (as
done by the FR keyboard) would be active on the EN keyboard.
Also, for the FR Keyboard:
- bring M key popup too when moving it to 2nd row.
- keep original ',' and '.' as on EN keyboard.
- add ';' instead of ',' as the added key, and let it have
  some key popup too, with keys helpful when CSS editing.

frontend/ui/widget/virtualkeyboard.lua

@@ -132,6 +132,9 @@ function VirtualKey:init()
             local key_function = self.key_chars[ges.direction.."_func"]
 
             if not key_function and key_string then
+                if type(key_string) == "table" and key_string.key then
+                    key_string = key_string.key
+                end
                 self.keyboard:addChar(key_string)
             elseif key_function then
                 key_function()