Feature/type annotation and docstring format

Description

This is a major refactor of the whole codebase, in particular with respect to the Docstrings and code readability.

Changes

In particular the decostring layout was changed from Numpy to Google style. Type hints were added to all modules and methods, making the type nameing in the docstrings unnecessary.

The changes includes an overall improvement of the documentation.

Overall, the code readability is improved and many PEP violations are removed.