Improve landing page on wiki for Developers

[Garbee]

The developers landing page is a lot of headings, lists, and links. For people jumping in, this seems hard to follow to actually get going.

Some quick ideas to help improve things:

1. Have an ordered list under a "Quick-start" section at the top to list the top say 4 or 4 total steps needed to get going. (grab code, build for platform, get in touch, submit patch.)
2. There are pages like MD5 Cert status that are pretty stale and don't really belong here. Maybe clean these links out and make the page as a whole more concise.
3. There are sections like "Practices". Maybe we should do something like developers/practices for this stuff. On that page also give a brief description about what that content is for. This would consolidate the top level page (and sections) into more of portals with descriptions to help new devs understand what those sections are specifically about. Making a fairly concise top-level landing page that is more friendly.

---

Yes, I'm storing this here even though it has nothing to do with Devtools Docs. Needed to not forget this stuff, I'll find the right place and move it out later.