[Timob-17744] iOS8: Feature to check if device can support touch ID

Additional feature that can be used to check if the device supports touch ID authentication. 
Sample code:

```javascript
	TiTouchId.deviceCanAuthenticate(
		function(e) {
			if (!e.canAuthenticate) {
				alert('Message: ' + e.error + '\nCode: ' + e.code);
				switch(e.code) {
					case TiTouchId.ERROR_PASSCODE_NOT_SET: Ti.API.info('Error code is TiTouchId.ERROR_PASSCODE_NOT_SET'); break;
					case TiTouchId.ERROR_TOUCH_ID_NOT_AVAILABLE: Ti.API.info('Error code is TiTouchId.ERROR_TOUCH_ID_NOT_AVAILABLE'); break;
					case TiTouchId.ERROR_TOUCH_ID_NOT_ENROLLED: Ti.API.info('Error code is TiTouchId.ERROR_TOUCH_ID_NOT_ENROLLED'); break;
					default: Ti.API.info('Error code is unknown'); break;
				}  
			} else {
				alert('device can authenticate');
			}
		}
	);
```