Remove RKCatalog server submodule reference
Drop RK prefix from entity names
Major overhaul to the Core Data managed object identification and relationship connection support.

* Replaces primary key with `RKEntityIdentifier`
* Add support for use of compound keys for object identification
* Refactor `RKConnectionMapping` to `RKConnectionDescription` and add support for connecting with multiple attributes
* Clarify naming of representation key methods to better match naming conventions
* Add type transformation support for object identification
* Greatly expand test coverage for object identification
* Drop the `NSEntityDescription` category
* Simplify the `RKManagedObjectCaching` protocol
* Add compound key support to the Fetch Request and In Memory Cache implementations
* Replace Kiwi with Specta for tests where contexts are helpful for organization
* Rename `defaultValueForMissingAttribute` to `defaultValueForAttribute`
Docs for RKConnectionDescription
Drop RKConnectionMapping, cleanup. Add predicate support
Docs cleanup
Header docs for entity identifier
Finish documentation for RKEntityMapping to cover Entity Identification and Connections
Add Apache license boilerplate to unadorned Core Data files
Drop the entity description category entirely
Add docs about using the user info to configure an entity identifier
Refresh Twitter examples and port to RKEntityIdentifier
Ensure RKConnectionDescription is Public
Add a 'Build All Examples' shared scheme to the Workspace
Merge branch 'feature/unify-primary-key-and-connections' into development
Bumping VERSION to 0.20.0-pre1
Tagging Podspec version
Switch to %ld and cast counts to long to suppress warnings on OS X
Fix crash when attempting to connect a one-to-one relationship that returns an empty result set
Merge branch 'release/0.20.0-pre1'