Refactor code for python packaging

[jyotishp]

Overview of changes to files

Moved the following

baselines -> neural_mmo/baselines
forge -> neural_mmo/forge
projekt -> neural_mmo/projekt
jsuarez -> neural_mmo/jsaurez
Forge.py -> neural_mmo/Forge.py
resource -> neural_mmo/resource
scripts/requirements.txt -> requirements/base.txt
scripts/rllib_requirements.txt -> requirements/rllib.txt

Building the wheels

The wheels can be built by running

git tag -am v1.5.1 v1.5.1
CLIENT_VERSION=1.5.1 python setup.py bdist_wheel

This does the following

1. Downloads https://github.com/jsuarez5341/neural-mmo-client/archive/refs/heads/v1.5.1.zip and extracts it to neural_mmo/forge/embyr.
2. Builds the wheel file with all the contents of the neural_mmo directory.