Make docstrings to be nice with pydoc

In some doc-strings we use formatting rules specific to Sphinx, but which make the interactive help (pydoc) to look bad.

This issue is about:

• defining how we should write some recurrent stuff, like documenting input parameters and return values.
• rewrite the doc-strings so they look fine on pydoc, even if that means losing some features with Sphinx, like cross references.

Note. If we had the resources, we would do like Python does, and document things twice: once in the doc-strings and a feature rich version in the rst files. But in any case the doc-strings must be usable with pydoc, so lets start with that.

Nenhum arquivo, teste ou ponto de entrada é especificado. Comece fazendo um inventário dos docstrings do projeto e comparando sua saída renderizada em pydoc com as convenções do Sphinx; considera-se concluído quando houver regras de formatação acordadas para parâmetros e valores de retorno recorrentes, além de docstrings reescritos que continuem utilizáveis no pydoc.