Fixed composer for sf2.2
Updatewd deps
Fixed typo
Trying to extend MenuItem, but perhaps not sensible

- MenuItem uses an associative array to store nodes, it is possible that
  this is not ideal for documents
Various improvements

- Support for fluid interface
- Factory class - allow creation of node from array
- ->toArray method on MenuItem
- Tests
Removed toArray, added serializer normalizer
Removed Factory from MenuItem

- Seems like extra complication at the moment and I am not very sure
  about it:
  - If hydrating from an array, will probably need the Document manager
    to find the content by its ID.
  - It crosses over with the SF serializer stuff
Menu normalizer denormalizes
Added docblocks
Removed menu factory
Reverted composer requirement, fixed tests
Fixed normalizer

 - Tested properly with my implementation now.
 - Removed @notsure annotations
Removed serializer
Comments and type hint
Renamed MenuItem > MenuNode
Oops, forgot to commit all the renamings
Added deprecated classes
Fixed deprecation annotations
Merge remote-tracking branch 'origin/master' into menu_as_knp

Conflicts:
	Admin/MultilangMenuNodeAdmin.php
adjust validation too