add chapter 18 and 19 for 4th edition (#1076)

* chapter 18 learning

* add chapter 19

* move init dataset in NN learner

* add adam optimizer, add nn learner

* remove cpt 19 for debug

* change while loop in games4e

* add chapter 19

* add sgd and adam optimizer

* add chpt19 deep nn

* add rnn

* add auto encoder

* add comments, correct tests

* add more comments, change algorithms according to orders of chapter sections

* add keras and numpy to requirements

* add tf as requirement

* add gc in test agent

* fix agent bugs for running test_agent and test_agent_4e together

* fix build error

* add chapter 21 and 22

* add chapter 12 and part of 13

* remove chapter 12 and 13, add test of rl

* modify rnn test

* fix build error

* Update utils4e.py