Clarify documentation for the wheel specification

Issue Description

I find the documentation extremely hard to read and time consuming. Very badly written.

Examples:

• In Binary Distribution Format section, Details chapter is before File Format chapter, making forward references to distribution-1.0.dist-info/WHEEL, distribution-1.0.data/. Some things are not defined at all, like what is purelib, what is patlib?

• In Overview of the Python Packaging, there is so little about the actual source and binary packaging and so much about Packaging Python applications. Packaging Python applications is just a discussion and its place should be in a Anexa or something, and not wasting reader's time with useless information.

How should documentation be improved

1. No forward references
2. Be concise and precise.
3. Move discussions to separate sections. There is a discussion section, but a lot of useless text for the reader is into the overview section as well.

Code of Conduct

• I am aware that participants in this repository must follow the PSF Code of Conduct.

Start with the Binary Distribution Format section, especially its Details and File Format chapters, then review Overview of the Python Packaging and Packaging Python applications. Clarify undefined terms such as purelib and platlib, remove forward references, and separate discussion from concise explanatory material. Done means the wheel documentation follows a logical order and addresses the three listed documentation goals.