Add standard cancel on login keypad

[mwfarb]

We should duplicate the pattern we are trying to use for canceling keypad up. On login with keypad up the upper left button Forgot Passphrase should be overlaid with Cancel. The keypad lower right Done button should execute the same action as the upper right done button: attempt to login.

[tenmalin]

When user press "return" on keypad, the app brings down the keypad. I think adding cancel button to replace Forgot Passphrase is too much and unnecessary.