Improve/automatic width and height for subtitles

@zenangst exactly, that's what I had in mind, but might be better than instead of having both notification registrations on Base, we could have

# HYPTextFormFieldCell
```
[center addObserver:self selector:@selector(resignFirstResponder) name:HYPFormResignFirstResponderNotification object:nil];
```
And 

# HYPPopoverFormFieldCell
```
[center addObserver:self selector:@selector(dismissPopover) name:HYPFormDismissPopoverNotification object:nil];
```