Fix cefpython3.wx package to work with latest v55+ #301

Currently cefpython3.wx package is disabled in setup installer. This package wasn't yet tested with latest v55+ releases. It will require some fixes and testing before enabling it back. There are plans to create a new CefBrowser widget (something similar to ChromeCtrl widget) for many popular toolkits like wxPython / pyQt / PySide - see Issue #312 for details. Creating new CefBrowser widget is prefered over fixing the old ChromeCtrl widget.