Open file list management dialog box.

def open_fileswitcher(self, symbol=False):
        """Open file list management dialog box."""
        if self.fileswitcher is not None and \
          self.fileswitcher.is_visible:
            self.fileswitcher.hide()
            self.fileswitcher.is_visible = False
            return
        if symbol:
            self.fileswitcher.plugin = self.editor
            self.fileswitcher.set_search_text('@')
        else:
            self.fileswitcher.set_search_text('')
        self.fileswitcher.show()
        self.fileswitcher.is_visible = True