OGM-454 Moving internal types to "impl" packages
OGM-454 Moving SPI types to "spi" packages
OGM-454 Moving OptionConfigurator to API package
OGM-454 Avoiding FQNs in JavaDocs of public types
OGM-454 Marking GridType and GridDialect#overrideType() with @Experimental
OGM-454 Extracting interface from class ConfigurationContext to avoid leaking impl types on SPI contracts
OGM-454 Splitting up ConfigurationPropertyReader into SPI and implementation part to avoid leakage of impl type on SPI contract
OGM-454 Moving some types intended for usage in dialects from "impl" to "spi"

* configuration context base classes
* option types
* id generators
* generic option model for dialects without options
OGM-454 Moving AssociatedEntityKeyMetadata next to other metadata objects into "grid" package
OGM-454 Moving generator types back to "impl", changing implementation of Neo4jSequenceGenerator to work with SPI only
OGM-454 Renaming DocumentStore{Entity|Property|Global}ContextImpl -> BaseDocumentStore{Entity|Property|Global}Context
OGM-454 Moving OgmEntityPersister to "impl"
OGM-454 Removing Instantiator contract from configuration reader SPI; Renaming ClassPropertyReaderContextImpl into DefaultClassPropertyReaderContext
OGM-454 Moving key and meta-data types to "key.spi"
OGM-454 Creating "model.spi" package for Tuple, Association etc., key types and meta-data types
OGM-454 Moving grid dialect operation context types to "dialect.spi"
OGM-454 Moving SchemaDefiner contract to "datastore.spi"
OGM-454 Creating "dialect.queryable.spi" package
OGM-454 Moving AssociationStorageConverter back to "impl"
OGM-454 Moving key and meta-data types to "model.key.spi"