Change foundation module to Google-style docstrings

[cemsbr]

The first module to be have its docstrings reviewed was the foundation one and it has standard Sphinx docstrings. Later, we decided to use Google-style docstrings because they are easier for humans to read. All the other modules have Google-style documentation. The specification can be found in https://google.github.io/styleguide/pyguide.html?showone=Comments#Comments.