Text field return bug fix

[plastus]

Fixes non-functional return key on keyboard when more than one text field is present in an alert controller.

E.g. password confirmation alert controller. After inputting text for the first field, tapping 'Next' on the keyboard resigns the keyboard and does not proceed to the next text field.

[jjessel]

@plastus , I think the same functionality could be accomplished by iterating through the textFields private property. Do you have a specific reason for the extension?