New opt: T.dot(A,B)[i] -> T.dot(A[i],B)
remove line not used.

It was used during development, but not needed at the end.
Preliminary version of dot+subtensor optimization, supporting arbitrary indexing.
Clarified docstring and removed unnecessary subtensor.
Tests for subtensor_of_dot, and corrected optimization for tensors with more than 2 dimensions.
Cleaner implementation of local_subtensor_of_dot.
Removed commented code.
Changed docstring for subtensor optimization
Merge pull request #2161 from paulfchristiano/dot_optimization

Dot optimization