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

# the platform name (PyV8, smjs, Mozilla, IE6, Opera, Safari etc.)
platform = ''  # to be updated by app, on compile

# a dictionary of module override names (platform-specific)
overrides = {}  # to be updated by app, on compile

# the remote path for loading modules
loadpath = None

stacktrace = None

appname = None


def setloadpath(lp):
    global loadpath
    loadpath = lp


def setappname(an):
    global appname
    appname = an


def getloadpath():
    return loadpath


def addoverride(module_name, path):
    overrides[module_name] = path


def addstack(linedebug):
    JS("""
        if (pyjslib.bool((sys.stacktrace === null))) {
            sys.stacktrace = new pyjslib.List([]);
        }
        sys.stacktrace.append(linedebug);
    """)


def popstack():
    JS("""
        sys.stacktrace.pop()
    """)


def printstack():
    JS("""
        var res = '';

        var __l = sys.stacktrace.__iter__();
        try {
            while (true) {
                var l = __l.next();
                res +=  ( l + '\\n' ) ;
            }
        } catch (e) {
            if (e != pyjslib.StopIteration) {
                throw e;
            }
        }

        return res;
    """)