Small improvements on Hotkey class

Two things:
- The hotkey class is not 100% consistent throughout all browsers. In some browser, keydown only gets fired once. In others it gets fired repeatedly as long as the users keeps the key pressed. I wanted to be able to make a keypress only happen once, or let it keep firing as long as the key is pressed. This had to work the same in all browsers. - I wanted to be able to disable the bubbling of pressed key events (this is convenient for eg firefox with 'search as you type' enabled).

I improved the Hotkey class a bit to meet these two demands, hope it's useful