Support for scalable font and gui elements

Fix positioning of tabheader in order to be usable for scaling GUIs
WARNING: this changes position of current tabheaders, mods have to adjust!

src/defaultsettings.h

@@ -22,7 +22,23 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 class Settings;
 
+/**
+ * initialize basic default settings
+ * @param settings pointer to settings
+ */
 void set_default_settings(Settings *settings);
+
+/**
+ * initialize default values which require knowledge about gui
+ * @param settings pointer to settings
+ */
+void late_init_default_settings(Settings* settings);
+
+/**
+ * override a default settings by settings from another settings element
+ * @param settings target settings pointer
+ * @param from source settings pointer
+ */
 void override_default_settings(Settings *settings, Settings *from);
 
 #endif