Added chain localizaton finder

- There are now two localization finders which handle when a webspace is
  present, and when a webspace is not present (as is the case with
  Snippets).
- The Chain localization finder will delegate to the appropriate finder.

- [x] test coverage
- [ ] gather feedback for my changes

__Informations:__

| Q             | A
| ------------- | ---
| Tests pass?   | yes
| Fixed tickets | (releated to snippets)
| BC Breaks     | no
| Doc           | 

This helper class should encapsulate all logic that can be mapped directly to Nodes. I.e. if we had a `Structure` (or `Page`, `Snippet`) object, then these methods would belong in that object.