Added TwoFactor Authentication (RFC4226)
Tested against Google-Authenticator app on Android 4.4.4

Made `verify_hotp` more efficient.

Added autofocus on twofactor input

Added GUI Unlock and Remove for TwoFactor credentials in /edituser/

Allow additional tries after elapsed time from last try exceeds configured parameter `$config['twofactor_lock']`.
If `$config['twofactor_lock']` is not defined or is set to `0`, administrators have to unlock accounts that exceed 3 failures via GUI.

Added Documentation

Moved TwoFactor form to logon.inc.php
Disabled autocomplete on twofactor input field
Updated Docs to include link to Google-Authenticator's install-guides

Moved authentication logic from authenticate.inc.php to twofactor.lib.php

typo in docblock for `twofactor_auth()`

Fixed scrutinizer bugs

To please scrutinizer
Merge pull request #383 from f0o/issue-365

Added TwoFactor Authentication (RFC4226)