Starting down the path of mini-batch support
Fixed the compute function for softmax in mini-batch mode
Fixed the backprop implementation for softmax in the mini-batch case,
when the cost function is *not* logloss
Fixed a compilation issue for softmax, and also fixed a bug in the
detection routine for which backprop algorithm softmax uses.
Made the logloss cost function support mini-batch
Made the sum squared cost function support mini-batch by converting it
to the mean sum squared cost
Fixed some of the residual bugs with mini-batch. There may be a
performance issue going on... need to investigate further.
Fixed some bugs related to mini-batch.

This seems to be having some stellar results with as few as a mini-batch
size of 4.