Build, documented page by page

The Build group now has a page for every screen in it — Projects, Versions and its tabs, Version dialogs, Primitives and types and Studio — with a light and dark screenshot of each tab and dialog. (#5622)

• Flags are marked. The git-like features (merge, fork, tag, the change report) are documented under a Flag offFEATURE_GITLIKE badge: they are switched off in every shipped build.
• Every page links its REST endpoints and CLI commands.