Issue #2288499 by er.pushpinderrana | jhodgdon: Fixed Action plugin classes need more docs links.
Issue #2226267 by yched: Improve default value handling of fields to be consistent (follow-up).
Issue #2286357 by tim.plunkett: Introduce Display Variants, use for the block rendering flow.
Issue #2216539 by jhodgdon, dawehner: Fill in @defgroup/topic docs for Views overview.
Issue #2216559 by jhodgdon: Repurpose @defgroup/topic docs for Architecture Overview.
Issue #2161801 by YesCT, vijaycs85, fran seva, batigolix, ifrik: Update hook_help for Config translation module.
Issue #2216563 by jhodgdon: Fill in @defgroup/topic docs for Object Oriented Programming overview.
Issue #2290285 by jhodgdon: Condition plugin classes need more links/docs.
Issue #2292025 by tim.plunkett: Convert BreadcrumbBuilderInterface applies() and build() to use RouteMatch.
Issue #2290253 by er.pushpinderrana: Make Archiver plugin developer info more discoverable
Issue #2290251 by er.pushpinderrana, amitgoyal, ParisLiakos, joshi.rohit100: Make Aggregator plugin developer info more discoverable
Issue #2290263 by joshi.rohit100, amitgoyal, er.pushpinderrana, cs_shadow: Make Filter plugin developer info more discoverable
Issue #2290279 by joshi.rohit100, er.pushpinderrana: Make RestResource plugin developer info more discoverable
Issue #2290271 by amitgoyal, er.pushpinderrana: Make Mail plugin developer info more discoverable
Issue #2290325 by cs_shadow: Get rid of form builder functions topic and references to it
Issue #2290435 by PQ: Fix broken link in robots.txt file
Merge remote-tracking branch 'origin/8.x' into mink-testing-2232861-larowlan