In recent years, Turkey has been seen as a bulwark of stability and democracy in a neighbourhood disfigured by political turmoil and communal conflict. But now, Turkey is wrestling with its own demons. Mass protests against the alleged authoritarianism of the Erdogan Government, have prompted a harsh police response. Stephen Sackur talks to leading Turkish writer and political activist Elif Shafak - what is Turkey's spasm of unrest really about?