Adding pakadge structure and inits

[asztalosors]

Create packages that are essential to a BES inference package.:

• emission --> package with scripts and codes that use deployed NN to infer emission from density. Further dev might include device-specific custom scripts: w7x, jet, east, ...
• density --> package with scripts and codes that use deployed NN to infer density from emission. Further dev might include device-specific custom scripts: w7x, jet, east, ...
• networks --> add the scripts and code necessary to generate and optimise NN of various flavours: elm, pinn, perception, ... and others
• utility --> should be a package that holds various utility functions that prep and curate data, download it

The expectation is that packages such as networks, density and emission should have well-defined universal data input and output formats --> allowing for any possible independent deployment of each. Utility aims to provide the tools to transform input data into the required format and other features.

[asztalosors]

ELM.py is relevant for further development of #5

[asztalosors]

evaluation.py is relevant for further development of #7.

[asztalosors]

pinn.py is relevant for the further development of #6