Bugfixes

#### Bugfix
Fixed a bug where 
```php
Aura\Marshal\Type\GenericType->$index_new
``` 
was not properly initialized.

#### New Tests
Added tests for empty Results of 
```php
Aura\Marshal\Type\GenericType->getChangedEntities() 
``` 
and 
```php
Aura\Marshal\Type\GenericType->getNewEntities()
```


##### Fixed Code Style Bugs