load_scores.py: read samples and targets (train and validation) from chosen score data
load_weights.py: function to load weights/vbias/hbias from a .pkl file
ffnn_fit_vel now uses load_weights and load_scores
Only load validation data if a validation dataset is given
lstsq_fit_vel.py: fit velocities using least-squares, loop through entire Magaloff/Batik datasets using one opus/KV as validation at a time