Move ResourceController model actions to separate methods.

[thomasowow]

As mentioned in #7 we constantly have to copy the whole method when only changing the model "action" part. The model action could be retrieving, storing, updating...

A new proposal is to separate these action calls in new methods so the overwriting is minimal. The following example would make this clearer.

// ResourceController
public function index()
{
    ... default stuff

    $models = $this->indexModel();

    ... default stuff
}

public function indexModel()
{
    return $this->resourceModelClass::paginate();
}

// My custom controller
public function indexModel()
{
    return $this->resourceModelClass::with('relation')->paginate();
}