extract CachingSupplierRegistry from InjectorBackedRegistry
- also used in SpringBackedRegistry
add method for invalidating caches in CachingSupplierRegistry
add tests for equals and hashCode methods
introduce RegistryBacking interface and remove SpringBackedRegistry and GuiceBackedRegistry
Merge pull request #435 from lhotari/caching-supplier-registry-pr

extract Registry implementation from InjectorBackedRegistry and SpringBackedRegistry