Fix wxHMI example after upgrading wxGlade

Newer wxGlade generates code to initialize GridSizer's with empty
elements.

...
grid_sizer_1.Add(self.window_1, 1, wx.ALIGN_CENTER, 0)
sizer_2.Add((0, 0), 0, 0, 0)
sizer_2.Add((0, 0), 0, 0, 0)
sizer_2.Add((0, 0), 0, 0, 0)
sizer_2.Add((0, 0), 0, 0, 0)
...

That causes following traceback, if new buttons are added
to already full sizer.

PLCobject : Traceback (most recent call last):

File "./Beremiz_service.py", line 389, in default_evaluator
res = (tocall(*args, **kwargs), None)

File "/tmp/tmpQS8ct2/runtime_0.py", line 540, in _runtime_0_start
wx.MessageBox(_("Please stop PLC to close"))

File "/tmp/tmpQS8ct2/runtime_0.py", line 504, in Init
lambda axis:( MakeButtonFunc(self, sizer, axis+"axisMinus"),

File "/tmp/tmpQS8ct2/runtime_0.py", line 502, in <lambda>
lambda btname: MakeButtonFunc(self, sizer, btname), ActionButtons)

File "/tmp/tmpQS8ct2/runtime_0.py", line 461, in MakeButtonFunc
print sizer, btname

File "/usr/lib/python2.7/dist-packages/wx-3.0-gtk3/wx/_core.py", line 14453, in Add
return _core_.Sizer_Add(*args, **kwargs)

PyAssertionError: C++ assertion "Assert failure" failed at
../src/common/sizer.cpp(1401) in DoInsert(): too many items (11 > 2*5)
in grid sizer (maybe you should omit the number of either rows or
columns?)


Tested with wxGlade version 0.8.3
Closes #41

# SOME DESCRIPTIVE TITLE.
# Copyright (C) is 21st century inquisition
# This file is distributed under the same license as the Beremiz package.
# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
#
msgid ""
msgstr ""
"Project-Id-Version: Beremiz 1.1\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2012-09-08 00:39\n"
"PO-Revision-Date: 2012-09-07 10:48+0100\n"
"Last-Translator: \n"
"Language-Team: \n"
"Language: \n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"X-Poedit-Language: French\n"
"X-Poedit-Country: FRANCE\n"
"X-Poedit-SourceCharset: utf-8\n"

# e69e0ee137df409290c6c6a5fbd512a6
#: ../../index.rst:4
msgid "Beremiz's documentation"
msgstr "Documentation de Beremiz"

# 7a5a9d62913b477b99421d5dc94a44be
#: ../../index.rst:6
msgid "Contents:"
msgstr "Contenu"

# 899ecb5f4ff84b8e98dbf5b1eaf7f393
#~ msgid "Indices and tables"
#~ msgstr "Index et tables"