* update conv kl-loss doc

* add the chinese doc of binary_cross_entropy_with_logits.

* Test SmoothL1Loss

* fix SmoothL1Loss doc

* fix some error

* fix to_tensor and add name=None,test=develop

* add cn doc of trace API

* add cn doc of functional ctc_loss and CTCLoss class.

* modified the format of doc.

* add en doc of ctc_loss and CTCLoss

* modified paddle.to_variable to paddle.to_tensor

* add api_cn

* test=develop

* add paddle.tensor

* add