* Merge agent & best practices doc. Plus other fixes
* Fix overly long lines
* Merge Getting Started and Basic Guides
* Rename guide and update links appropriately
* Fix broken link
Merged the "Overview" sections of a few pages into their respective sections in ML-Agents-Overview:
- Training-Using-Concurrent-Unity-Instances.md
- Training-Self-Play.md
- Training-SAC.md
- Training-PPO.md
- Training-Imitation-Learning.md
- Training-Environment-Parameter-Randomization.md
- Training-Curriculum-Learning.md
- Reward-Signals.md
- Feature-Monitor.md
- Feature-Memory.md
Organized ML-Agents-Overview into Training Methods and Training Options sections.
Follow-up action items (part of a separate PR):
- Smooth over the documentation in ML-Agents-Overview (right now, we somewhat just pasted text from other pages). If we align on the new structure for this page, we can iterate on it.
- Update “Key Components” section with new graph and discuss side channels and revise use of Academy.
- Consolidate “Training-*” docs into Training-ML-Agents to offer a single guide for all hyperparameter selection