Use list to save memory

Get cuda-convnet repository path from CUDA_CONVNET;
Use list (packs) to save memory with metadata;
Use CIFARDataProvider defaults (32, 32) in ccn-make-batches;
Fix image orientation in ccn-make-batches;
Save CSV header in write_predictions;
Let metadata be optional;
Fix ValueError exception with multi-label classifiers in report.