* add back ability to create transform with loader
* change 'samples' -> 'examples' for tfds wrapper to match tfds naming
* add support for specifying feature names for input and target in tfds wrapper
* add class_to_idx for image classification datasets in tfds wrapper
* add accumulate_type to avg meters and metrics to allow float32 or float64 accumulation control with lower prec data
* minor cleanup, log output rate prev and avg