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'

<?xml version="1.0" encoding="ISO-8859-1" ?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            xmlns:xhtml="http://www.w3.org/1999/xhtml">
  <xsd:element name="Python">
    <xsd:complexType>
      <xsd:annotation>
        <xsd:documentation>Formatted text according to parts of XHTML 1.1</xsd:documentation>
      </xsd:annotation>
      <xsd:sequence>
        <xsd:any namespace="http://www.w3.org/1999/xhtml" processContents="lax"/>
      </xsd:sequence>
    </xsd:complexType>
  </xsd:element>
</xsd:schema>