ImportCSV parse error; further integration

ImportCSV didn't handle embedded delimiters and quotes within quotes
well. It should now handle these with a slightly new and smarter
routine. This method (ImportDialog.ParseLine) is well commented too.

ImportCSV and Salstat are more closely integrated now. Loaded CSV files
now trigger the unsaved data flag (self.grid.Saved). The cancel buttons
work as intended too. ImportCSV file open dialog should display proper
icon and begin with more sensible values.