Big Refactoring

- This PR changes the role of [Menu|MenuNode] to the standard
  implementation - "the document that integrates with other CMF
  components" whilst MenuNodeBase simply makes KnpMenu persistable and
  adds nothing more.

- The Multilang specific classes have all gone.

- There are now only 2 admin classes - both for the standard
  implementation
Tests are working but translations are not!
Tidied up and added show test
Reverted show change
Removed "getBlocks"
Updated CHANGELOG
Merge pull request #101 from dantleech/change_to_base

Big refactoring of document roles