FEATURE #553 [SnippetBundle] Possiblity to show all snippet types

Default behavior when no snippet type is selected is now to show all snipet types.

_Tasks:__

- [ ] test coverage
- [ ] gather feedback for my changes
- [ ] submit changes to the documentation
- [ ] ... <add your own tasks>


__Informations:__

| Q             | A
| ------------- | ---
| Tests pass?   | ywa
| Fixed tickets | #553 
| BC Breaks     | Default behavior is now to allow selection of all snippet types (instead of falling back to restricting on the default snippet type)
| Doc           |