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.

未指定任何檔案、測試或進入點。首先盤點專案中的 docstrings，並將它們在 pydoc 中的轉譯輸出與 Sphinx 慣例進行比較；完成的標準是：已就重複出現的參數和回傳值制定一致的格式規則，並且重寫後的 docstrings 仍可在 pydoc 中使用。