Theano benchmark additions

Some changes to the Theano benchmark:
* Made implementation of "average over 10 trials" consistent with code again, fixing 229d52e (it did the correct thing for this special case, but `number` and `repeat` did not control what they said any longer)
* The experimental `GpuCorrMM` is timed in two modes: With automatic insertion via graph optimization, and with manual insertion (the latter should be close to caffe, the other one may be faster or slower for some configurations because it sometimes chooses a different code path)
* The cuda-convnet wrapper is tested with `partial_sum=None` as before (the memory-saving setting) and `partial_sum=1` (a more memory-hungry setting that is a lot faster for the gradient wrt. weights for some configurations)