refactor(driver-compat) TypeMapping -> DBObjectFactory
refactor(driver-compat) rename DBCollection.codec to DBCollection.objectCodec
style(driver-compat) fix Checkstyle warnings in DBCollectionTest and CollectibleDBObjectCodec
chore (driver-compat) move spock tests to 'unit' subdirectory of 'test'
fix(driver-compat) make DB.executeCommand not wrap a org.mongodb.MongoCommandFailureException