UITextField: remove custom canPerformAction(action, withSender:sender)

Hi,

I ran into troubles with ```UITextField``` regarding the double-tap(?) menu (select,select all, paste) which did not appear even when ```editable: true``` is set for the row.

After checking the formotion source I think ```canPerformAction(action, withSender:sender)```is the reason: Either it is true, then all available menu options (including "take a photo"…) will shown but by default no menu is shown.

Removing this method makes UITextField using its defaults which are sane (e.g. allow a user to select/copy or paste content again).

<img src="http://i.imgur.com/qhLkd2p.png">

Maybe there is a better idea to fix this problem. I have no idea, sorry :(