Expose connected user data in wp.getOptions

To help the mobile apps help the user figure out which wp.com account
they're connected to, include user ID, username, and email in
wp.getOptions.

Also includes number of sites so the app can decide if it should suggest
Jetpack Manage.

See previous discussion in #1305
That would make sense. If you look at `wp_getOptions`:

```php
// If no specific options where asked for, return all of them
if ( count( $options ) == 0 )
	$options = array_keys($this->blog_options);

return $this->_getOptions($options);
```

I think it'd make more sense to add our stuff to `$wp_xmlrpc_server->blog_options` here and just return `wp_getOptions( $args )`