Refactored get_cost_gparams methods of auto-encoders to return just tuples of (param,gparam) so that different parameter updates schemes can be applied.  Also added three methods to SdA to do parameter updates: sgd_cm for classical momentum, sgd_adagrad for AdaGrad, and sgd_adagrad_momentum for an AdaGrad variant where the sum does not continue to increase but is instead a weighted sum over a given windowsize.