Use NSTableView for changing hotkeys in Preferences

Don't know if you like it or not, I'm sorry if you don't, but during adding a row to Hotkeys tab in Preferences, I felt it's a bit of pain to layout new labels and SRRecorderControl correctly.

So the proposal is to use NSTableView and programmatically populate these controls. I guess I should have discussed about the change before sending a pull request, but the code was done while I was learning and playing to see how well it'll fit. Please feel free to reject and close if you don't like the approach.

Note that I've made it not to look like an NSTableView but keeps exact the same visual as before. I could change them back to look like an NSTableView if you like, either now or in future when you'll need scrolling behavior.

For now, I think the benefits are easier to layout, with exactly the same pitch, and easier to maintain, so I chose not  to change the visuals as much as possible.

I hope you like it.