Merge tag 'v1.20.0' into develop

Full support of deep convolutional neural network.
Add order prerequisite: mkdir -p obj/ if not exist.
[Refactoring] Remove deprecated codes in nn-train
Add Features in README.md
Data transposed. All example.sh tested.
Add const feedForward method in nnet.
Merge branch 'feature/transpose-data' into develop
Remove deprecated codes in FeatureTransform.
[New Feature] Tanh, ReLU, Softplus non-linearities.

Tanh, ReLU, Softplus checked and workable.
But softplus converge really slow and perform awfully.
[New Feature] Initialize empty model after reading.

User can now use nn-init create blank neural network topology. Class
NNet will try to initialize the empty weight after reading. It's more
convenient to add dropout or change non-linearity now.
[Bug Fixed] tanh explodes when exp(x) too big.

Add brief explanations for each example.
Add non-linearities as new features in README.md
Merge branch 'feature/new-nonlinearities' into develop
Merge branch 'release/v1.25'