Issue #2216549 by jhodgdon, steveoliver: Fill in @defgroup/topic docs for Render overview.
Issue #1898070 by benjifisher, jjcarrion, LinL, idflood, joelpittet, oshelach, tlattimore, Les Lim, sergey.semashko, jesse.d, bdgreen, jenlampton, Cottser, duellj, artofeclipse, vlad.dancer, steveoliver, EVIIILJ, c4rl, elv, OpenChimp: File.module - Convert theme_ functions to Twig.