Added a page on Branding

1 new page with a brief description of recommended use of the terms and
logos plus a link to it is the site navigation.
IMHO it doesn't belong in the sidebar or footer at all. I think making the page easily discoverable would send the wrong message, that D is too concerned with issues such as branding than actual quality of the language or implementation.

What other programming languages advertise a page like this on their home pages?

I suppose it could be useful to have some agreed-upon conventions written down, but they are more useful to people within the community, people working on projects related to the language itself. For such cases, we can post a link to the page in the discussion whenever the situation arises.