Runtime: wx.app.mainLoop and twisted reactor now share main thread with runtime.Worker.

This fixes exception when invoking python interactive shell from Runtime's tray
icon right-click menu.

Probably a consequence of wxPython upgrade, together with initial bad idea to
move wx.app.mainloop in non-main thread.

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# This file is part of Beremiz
# Copyright (C) 2019: Edouard TISSERANT
#
# See COPYING file for copyrights details.

from __future__ import absolute_import
from svghmi.svghmi import *