Support abstract complexTypes - abstract modifier generating

In depend of issue https://github.com/wsdl2phpgenerator/wsdl2phpgenerator/issues/123 I've added a abstract modifier support in this commit, tests included. Hope, you'll agree.
Yes. Creating instance is apperead once but the $typy var is used later. Would you like to have a code:
```php
$type = new ComplexType($this->config, $typeNode->getName());
$type->setAbstract($typeNode->isAbstract());
```
I think, it's not neccesary.