Add covariance matrix function theano.tensor.cov

Add some tests, to check at least if everything runs well.

Standardize all three files (dnn_fwd, dnn_gi),
to have same code logic and organization across these three codes.

Add fallback entries as fallback functions.

Add `-t` to hash for timed algorithms.

Specifying culprit node in `MissingInputError`

Spatial Transformer Network Ops using cuDNN

Add g++ "-WL,-rpath" argument for CTC ops.

separate copying inputs and copying orphans

Adding tensor6 and tensor7 constructors

Update conv doc.

phase out outdated conv3d