[Cocoapsql-developer] commit; Auto set the 'Connect', 'Disconnect' and 'Export' menu items enabled/disabled:

[Olaf v. O. <ol...@ad...>]

Auto set the 'Connect', 'Disconnect' and 'Export' menu items 
enabled/disabled:
  I added the actions to the first responder of MainMenu.nib
	menuConnect:
	menuDisconnect:
	raiseConnectionSettingsWindow:
	doExportMenuAction:	(for consistancy reasons)
and reconnected the Connection-menu items to these actions in the first 
responder.

To auto Enable menuItems, I have made PSQLController the delagate of the 
mainWindow.

Added to PSQLController.m
- (BOOL)validateMenuItem:(NSMenuItem *)menuItem {
	SEL action = [menuItem action];
	if (action==@selector(menuConnect:) && [connection connected]) {
		return NO; }
	else if (action==@selector(menuDisconnect:) && ![connection 
connected]) {
		return NO; }
	else if (action==@selector(doExportMenuAction:) && ![tableView 
numberOfRows] > 0) {
		return NO; }
	else {
		return YES;
	}
}