Fixed a bug reported by cityhall consisting in not calling tensor.as_tensor on arguments before calling make_node

implement/test the proposal that created shared variable must return the same type as what they received as input.

Add test for inplace operation on shared variable when the shared constructor input is casted to the same value as the internal type.

this will allow building the library cuda doc on our webserver

This is not 'sandbox documentation' as in docs that are no good - this is good
documentation for code that is in the sandbox.

Split Josh's documentation between aliasing.txt and CudaNdarraySharedVariable.set_value docstring note.

test that we work inplace when accessing the internal of theano to replace the value of a shared variable.

For tensor and sparse shared varible, test that we don't work inplace.(not implemented for now)

I am not sure why this is necessary now.  One guess is that the canonicalizer or
something else has been modified to put in identity(), and now it is more
obvious that we need an optimization to take it out again.  I'm hoping that this
improves the slowdown recently observed in convolutional net benchmark.

The modification ensures that that even if numpy is clever enough to not make a
copy on unit-length reductions, the perform() returns a copy.

Corrected DEBUG_MODE and FAST_COMPILE tests for grad of Prod. Added comments on mechanism for this grad.

fix may_share_memory for sparse type as it was done for ndarray type. Add may_share_memory test for CudaNdarray type