Add a Clone button in clock edition

The Clone button creates the 'same' Event just after the selected one (same length, same Event name) : 

![rivendell-rdlogmanager-editclock-clone](https://cloud.githubusercontent.com/assets/24570/4379854/70143f86-4364-11e4-9bf5-1741f8ad5103.png)

Is there any reason to assign to `line` twice? Other than that's how the old code does it, and that should be fixed too?