Op doc merge

Conflicts:
	doc/cifarSC2011/extending_theano.txt
	doc/extending/op.txt

moved import cuda where I need it.

function

Op documentation

More explicit error message

Makes it more obvious to users what may be their mistake when they get a
TypeError after trying to index a shared variable.

Op doc

Due to lack of experience with git, I'll merge this pull request and send another one that fixes all the bugs I've seen.

Added 'pass' method bodies.

Thunk hook refactor

Check compile/run-time kernel dim mismatches raise an error.

Spelling + spacing fixes