Removed Easymongo.Database.Adapter class. This class is no longer useful with recently-refactored
constructor dependency injection. Refactored/Simplified ctors of EasyMongo.Database classes. Renamed files
housing EasyMongo.Database classes to properly reflect their enclosed types. Added EasyMongo.Contract.IReader<T>,
EasyMongo.Contract.IReaderAsync<T>, EasyMongo.Reader<T>, EasyMongo.ReaderAsync() as experiment in investigative usefulness.