Allow native Laravel validation

[rtrzebinski]

https://laravel.com/docs/5.3/validation#validation-quickstart

Currently we can't use the following syntax in controllers:

$this->validate($request, [
    'title' => 'required|unique:posts|max:255',
    'author.name' => 'required',
    'author.description' => 'required',
]);

Problem is that Laravel uses 'errors' session variable to store validation errors, while Nodes uses 'error'. Because of this Nodes backend views can not see errors. Fix is to change view(s) to use 'errors' instead of 'error'. This is breaking change so major release number should be increased.

[Casperhr]

Maybe we should for now have support for errors and error

And then deprecate error.