fix issues in PLCOpenEditor with moving from wxWidgets 2.8 to 3.0

1)
./PLCOpenEditor.py:63: wxPyDeprecationWarning: Using deprecated class PySimpleApp.
app = wx.PySimpleApp()

2)
./PLCOpenEditor.py:475: wxPyDeprecationWarning: Call to deprecated item.
wx.InitAllImageHandlers()

3)
Traceback (most recent call last):
File "./PLCOpenEditor.py", line 480, in <module>
frame = PLCOpenEditor(None, fileOpen=fileOpen)
File "./PLCOpenEditor.py", line 163, in __init__
IDEFrame.__init__(self, parent)
File "/tmp/f/beremiz/IDEFrame.py", line 657, in __init__
self._init_ctrls(parent)
File "/tmp/f/beremiz/IDEFrame.py", line 485, in _init_ctrls
self._init_icon(prnt)
File "/tmp/f/beremiz/IDEFrame.py", line 476, in _init_icon
if self.icon:
AttributeError: 'PLCOpenEditor' object has no attribute 'icon'

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          <xsd:attribute name="Command" type="xsd:string" use="optional" default="make -C %(buildpath)s all BEREMIZSRC=%(src)s BEREMIZCFLAGS=%(cflags)s MD5=%(md5)s USE_BEREMIZ=1 FROM_BEREMIZ=1"/>

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