Clean up font management

Default to b.userName instead of message->account()
Made font updatable in the Settings dialog with a font dialog
More work on subscription badge loading

Known issues:
  - Font isn't updated in a split until a new message is written in that split
  - When font/font size is changed, old messages don't have their size updated causing weird layout of old messages

src/twitch/twitchmessagebuilder.cpp

@@ -95,7 +95,7 @@ SharedMessage TwitchMessageBuilder::parse(const Communi::IrcPrivateMessage *ircM
 
     iterator = tags.find("display-name");
     if (iterator == tags.end()) {
-        displayName = ircMessage->account();
+        displayName = b.userName;
     } else {
         displayName = iterator.value().toString();
     }