Patch for list_editor with the qt4 backend

I implemented a patch for the list editor making it compatible with PySide. It does correct the issue of the example. I used a QSignalMapper to identify the sender. I asked the QSignalMapper to send an int to the call back function. This int is used to get the sender from a list storing all the IconButtons. I had to proceed that way as it seems that both under PyQt4 and PySide the QSignalMapper is broken and does not emit the 'mapped' signal when asked to send anything else than an int (ie a string, or a QWidget). I used the new style connection syntax for Qt. I also corrected a small issue in menu causing PySide to create not only an action but also a sub menu for each line in the menu description. In helper I just switched to new style signal/slot connection.