projects: Fix CWL home page link.

Thanks to Stian Soiland-Reyes for pointing this out.

projects: Improve alt text throughout.

* The project logos don't add to the content, so empty their alt text.
* Improve the flow of Donate button alt text.

projects: Move project logos below <h2>s.

The underline of <h2> was running through the project logos before.

Rename members directory -> projects directory.

As part of the transition to have the canonical URL for member projects
be "projects" instead of "members", rename the directories.

The following rewrite rule will be needed in Apache configuration now:
RewriteRule ^/?members?/index.html$ supporter/ [L, R]
RewriteRule ^/?members?/(.+)$ projects/$1 [L, R]
RewriteRule ^/?members?/?$ supporter/ [L, R]