Update documentation files in the project root

Outdated or redundant information has been removed, some useful new information has been added. The Markdown files now all start with the same hyperlink. Especially the [Readme](https://github.com/the-xkcd-community/the-red-spider-project/blob/master/Readme.md) has been rigorously [rewritten](https://github.com/jgonggrijp/the-red-spider-project/blob/791de9eaba667c0c900c5cc471152a47023e56c9/Readme.md).

Feedback would be very much appreciated.