fix splash loading with wx3.0

Previously only gray square was shown. Apparently to show splash screen several calls of wx.Yield() are necessary.
Unfortunately splash.IsShowOnScreen() returns always 1 regardless of whether splash is on the screen or not.
this fix is a dirty hack. It just process all events after splash is created during 0.3 seconds.

These classes are intended for use server-side.

e.g. in a django view.py :

    from pyjs.jsonrpc.django import JSONService, jsonremote

    jsonservice = JSONRPCService()

    @jsonremote(jsonservice)
    def test(request, echo_param):
         return "echoing the param back: %s" % echo_param