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.
CS fixes
Merge branch 'feature/chain-localization-finder' into feature/page-refactor

Conflicts:
	composer.json
	src/Sulu/Component/Content/Mapper/ContentMapper.php
	src/Sulu/Component/Content/Mapper/LocalizationFinder/ChainFinder.php
	src/Sulu/Component/Content/Mapper/LocalizationFinder/NullWebspaceFinder.php
	src/Sulu/Component/Util/SuluNodeHelper.php
Merge remote-tracking branch 'origin/feature/page-refactor' into feature/page-refactor