FB Connect modal; put create and connect existing account all in the same modal

The old version of FB connect displayed a modal when users choose to login via the user menu.  This modal allowed them to create a new account, or click a button that would take them to a sign in page.  Rather than split the experience, put create and sign-in in the same modal.

https://wikia-inc.atlassian.net/browse/UC-111
Since a return in either of these fields will submit the form rather than add a new line to these input fields, it might be more clear to use getVal, e.g.:
```php
$this->getVal( 'username', '' );
$this->getVal( 'password', '' );
```