Improve feature provider option descriptions

At this point the [descriptions of the plugin options](https://github.com/lgeiger/ide-python/blob/master/package.json#L67-L350) visible in the Atom settings are rather basic and often less accurate than what can be found in the documentation of the specific feature provider.

We should improve those descriptions and/or link to the relevant docs if applicable.

Any help on this is highly appreciated. This issue doesn't need to be fixed in one go, we can iteratively improve the plugin documentation.

Start with the plugin option descriptions in package.json, especially lines 67-350, and compare each entry with the documentation for its specific feature provider. Update descriptions or add relevant documentation links where they are inaccurate or too basic. Done means the Atom settings descriptions are clearer and more accurate for the options reviewed.

Written by the indexing model from the issue text.