Update annotations of layers.py

refine MKLDNNLayer

remove ProtoData

* Improve the initializer Interface for fc, sequence_conv and conv2d layers
* Fix some typos in python code
* Fix CI

Add maxout operator.

and remove some comments.

add the softsign activation.

fix bug (conv2d  groups: 'num_channels % groups is not 0:' )

enable mkldnn benchmark with googlenet

Fix pool max with index.(Mask type should be int, not float)

Add cudnn pool3d

Add sequence slice operator

remove redundant tests in layer helper's unittest.