Filewindow panels - most widgets

AddDataPanel and EditDatabasePanel created as inheriting from
DatabasePanel
Buttons added
Placeholder widget methods (so that the GUI side is sorted - now these
should be fairly easy to hook up to the database without having to
search for the correct wxPython event handlers, object methods etc)
OnFileExample method - when you highlight a row and press Enter on the
keyboard, it can do stuff using strings from the table

To follow - disable text editing of elements of fileList; enable
drop-down-box-like behaviour of most columns; consider checkbox-like
behaviour for most columns