Preliminary changes to support COCopier in EtoileUI (mostly bug fixes)
Added -initWithEntityDescription:UUID:objectGraphContext:
Fixed COCopier to support collections of value objects.
Added -willDiscard to COObject
Fixed COColorToHTMLString for nil value
Added COClassToString transformer
Report incorrect transformer name with an exception during serialization
Fixed serialization transformers for elements of multivalued properties
Finished to fix serialization transformers to support elements of multivalued properties.
Raise exception if -contentKey is not overridden when necessary
Fixed test failure introduced with previous commit
Fixed collection serialization to ensure transformers are called even when elements are nested collections.

Note: for example, this means a set can contain dictionaries representing simple objects, and these dictionaries are serialized as plists.
Fixed binary serialization for big blobs
Updated serialization to use -persistentType and -type as necessary
Added small code snippet to TODO
Fixed loadedObjectsForUUIDs: to skip additional store item UUIDs rather than crashing

[[ctx loadedObjectForUUIDs: [ctx changedObjectUUIDs]] is now supported, even when some inner object declares a persistent keyed property.

Note: In the long run, -changed/inserted/updatedObjectUUIDs should be renamed to -changed/inserted/updatedItemUUIDs to increase the API consistency.
Added NS_RETURNS_NOT_RETAINED to methods that don't return retained arrays, when they are expected to due to the 'copy' prefix
Reworked dictionary serialization to get the copy support working without -[COItem additionalStoreItemUUIDs]

Fixed incremental update to dictionary items without updating the owner item. For example, [objectGraphContext addItem: dictionaryItem] now works.

Note: Attribute dictionaries can be accessed in -awakeFromDeserialization, as it was the case previously.
COSerialization: Enable sanity check of serialized reference type (ETUUID is composite or non-composite, COPath is non-composite) in -objectForSerializedReference:
Merge pull request #10 from etoile/serialization-rework

Serialization rework