Modified argmax() method of
    * MultilabelModel
    * HashedMultilabelModel
to give correct value of ret->score
Merge branch 'develop' of https://github.com/shogun-toolbox/shogun into hashed-mutlilabel
updat the interface
bug fix
add dual likelihood
update the existing KL methods
update the unit test
CART optimized
update the existing kl methods and dual likelihood
Merge pull request #2347 from mazumdarparijat/gd

CART optimized
Added abstract base class CFeatureSelection
Merge pull request #2353 from khalednasr/autoencoders

Implemented deep autoencoders
minor change in RandomCART
Merge pull request #2350 from yorkerlin/develop

update and add dual likelihood
Merge pull request #2352 from lambday/feature/selection

Added abstract base class CFeatureSelection
Merge pull request #2355 from mazumdarparijat/documentation

minor change in RandomCART
add the dual KL method
* Minor bug fix in MultilabelModel.
* Added multilabel_structured_prediction notebook.
cleared all outputs of the multilabel_structured_prediction notebook
Merge pull request #2356 from yorkerlin/develop

add the dual KL method