Add wxListItem generator, child of wxListView

[KeyWorksRW]

Description:

ListViewGenerator has a contents property for initializing strings in a wxListView, but each item lacks the ability to set color, font, state, bitmap, etc. What would be ideal is to have a gen_wxListItem which can only be a child of a wxListView. This would allow the user to have much greater control over what gets added to the wxListView. Even if the user doesn't ultimately use it to populate the wxListView, generating the code for a single item should make it easy for the user to understand what they need to do in their own app.