Use KeyDown for shortcuts

I just encountered an interesting UX issue regarding pressing a shortcut. I was using the KeyUp event for some of the shortcuts, and I've found it to be flaky and counter-intuitive.

The main reason is that it's rather difficult to trigger the key up event when the shortcut consists of 2 of more keys. Think about it. When we want to trigger the shortcut Ctrl+C, we don't really ensure we press Ctrl while lifting the C key. It's more likely that we lift both keys at the same time, and many times you might lift the Ctrl key before the C key.

The secondary reason is that, in other apps, the keys are fired at the KeyDown event. Typing is one example of this.