[WIP][FEATURE] adjustments on widgets

__Tasks:__

- [ ] gather feedback for my changes

__Informations:__

| Q             | A
| ------------- | ---
| Tests pass?   | yes
| Fixed tickets | none
| Doc           | none

__ Requires:__
- https://github.com/sulu-cmf/SuluAdminBundle/pull/129
- https://github.com/massiveart/husky/pull/335
@michaelzangerle Actually we should add some more information to these exceptions, like which Widget caused it, which parameter was wrong, ... (same goes for the `WidgetEntityNotFoundException`).