Added a switch in the generation of updates for SdA pretraining functions so that un-tracked parameters don't get updated.  I'm not sure if this is quite the right thing to do: the biases of the dAs will not be updated with momentum, but the model parameters shared with the MLP will.
Added a switch in the generation of updates for SdA pretraining functions so that un-tracked parameters don't get updated.  I'm not sure if this is quite the right thing to do: the biases of the dAs will not be updated with momentum, but the model parameters shared with the MLP will.

lzamparo/SdA_reduce,lzamparo/SdA_reduce,lzamparo/SdA_reduce