Relation improvements

• Fixed issue #4 (Embed relations where recreated on every update)
• Breaking change: Renamed CDKWithoutId to CDKEmbedding
• Breaking change: Renamed CDKRelatedById to CDKReference
• Breaking change: Removed CDKNoMapping, use the new CDKMapStrategy instead

Observation helper and debug methods

• Created ManagedObjectObserver: Easy observation of managed object changes
• New dumpImportConfiguration method on CoreDataStack to show import config
• New debugDump method on CoreDataStack to show current stack

First stable-ish release

Saving, fetching, updating, importing. Most of the basics are available!