Rec automatic optimization, special behavior of layers

A list of layers with special behavior when inside a recurrent loop vs outside recurrent loop (optimized out of the loop).

• RecLayer / RnnCellLayer. Inside loop, they have hidden state, and do one step. Outside loop, they operate on the time sequence. Determined whether the input has a time dim.

• TwoDLSTMLayer

• SelfAttentionLayer (deprecated)

• KenLmStateLayer

• EditDistanceTableLayer

• MaskedComputationLayer

• UnmaskLayer