check error level in error handler

Yii2 error handler does not take into account current error reporting level.
For example current code will raise error handler and it throw exception, despite of disabling notices.
```php
error_reporting(error_reporting() & ~E_NOTICE);
$a = ['foo' => 'bar'];
echo $a['baz'];
```
Also I've omit error levels in `set_error_handler` and attach Yii2 handler to all error levels, because at runtime error reporting level can be changed to anything and error will not be handled.