Fix assert import

A few typo fixes in doc

Important fix
Everything looks good

We should always use the convention name for input to function that we override!

There is more fix that are missing.

We call the shape_feature.on_attach with an empty env to help prevent change to the shape feature request change to the scan infer_shape.

I made a registration system that allow all Theano Type to tell if they allow OutputGuard to generate c code for them. This fix the dependency on sandbox code in theano/compile/mode.py file. This make it a better fix then what was done for SparseType.

Added test.

Fix extract diag

Fix sparse dot

Composite fixes

But they cause a mysterious bug in test_gpu_fusion on my mac in which the second
of cases 2 and 3 (any order) fails to update the result buffer. I tried but
failed to fix it so far.

Adding tag traces is expensive. This PR disables adding tag traces during the
optimization process itself, which is anyway not the point of tag traces. This
saves 10 seconds of compilation on a graph I'm working with that ends up with
about 240 nodes.