Issue #2702537 by ifrik, Wim Leers: Update the BigPipe module description to be in line with the Help text standard

Issue #2469431 by Wim Leers, Fabianx, swentel, nod_, yched, dawehner, tstoeckler, catch, borisson_: BigPipe for auth users: first send+render the cheap parts of the page, then the expensive parts