Organiziaton of documentation for installs - docker vs. non-docker / official vs. unofficial

[codinghorror (Jeff Atwood)]

As for the proposals:

1. Done!

2. I just deleted that old meta howto topic as it was out of date anyway. So all install docs are on GitHub now.

3. I think we should alias INSTALL-digital-ocean.md as INSTALL-cloud.md to generalize it but I am unsure how to do that.

4. We already do, I believe. (see image below)

5. Can you point to howto topics that you think should be moved?