CrazyAra 0.4.0

This version went live on 2019.02.13 on lichess.org: https://lichess.org/@/CrazyAra

Please put the file model-1.25948-0.589-0246.params from release CrazyAra 0.3.1 in the directory CrazyAra_0.4.0/model/params/.
The weight file of the neural network is uploaded separately to avoid additional upload cost when only changing source code.

Improvements for MCTS search

Added conservative, pessimistic check for q-values along search path by adding:

q_future, indices = self.get_last_q_values()

Score of CrazyAraFish-0.4.0 vs CrazyAraFish-0.3.1: 21 - 9 - 0 [3 min/40 moves]
Elo difference: 147.19 +/- 147.79

30 of 30 games finished.

Additionally, major refactoring thanks to @Matuiss2.

2019.03.28: Updated default MCTS search parameter to "context": "cpu", "threads": 8, "batch_size": 8, "neural_net_services": 1 for better initial settings on most hardware.

2019.05.30: CrazyAra_0.4.0.zip; mcts_agent.py: Removed unused import of library gevent. Updated version id.