Entity Hydrate

this is my proposal to handle the solr result hydration. so anyone can now listen to the "solr_hydrate_entity" event and hydrate by its own.

with stopPropagation it is possible to interrupt/prevent a multi hydration
```
$event->stopPropagation();
```

by the way, it isnt a good idea just create a new entiy, what about entitys with constructor they need parameter ? and i miss a caching system for the meta entity infos