Don't load the default AppName class as kv file

[rvanlaar]

Please consider adding the following code to the Kaki App.
This fixes a bug where kivy autoloads the {app}.kv file which falls out of scope and results in duplicate content being drawn.
The autoloaded UI can't be updated and will be drawn for the duration of the app lifecycle.

    def load_kv(self, filename=None):
        """
        Don't autoload the appname .kv file when in debug mode
        due to the autoloaded .kv file being drawn but not bound to the code, resulting in stale pixels on the screen.
        """
        if self.DEBUG is True:
            return False
        return super().load_kv(filename=filename)