Issue #2985147 by eliclaggett, msankhala, neclimdul: Correct copy pasted plugin constructor documentations

(cherry picked from commit 8c5075ad)

Issue #2719695 by alexpott, Mile23: Fix 'Drupal.Classes.ClassDeclaration.CloseBraceAfterBody' coding standard

Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #1392754 by tss, justAChris, jhodgdon: Comply with new documentation standards for @file for namespaced class files

Issue #1875996 by Xano, tim.plunkett, neclimdul, Rajendar Reddy, Jalandhar: Reconsider naming conventions for derivative classes.

Issue #1874498 by tim.plunkett, dawehner, jibran, benjy: Provide and use API methods for retrieving base plugin and derivative names from block plugin IDs.

Issue #1986802 by yched: Rename PluginInspectionInterface::getDefinition() to getPluginDefinition().

- Patch #1497366 by neclimdul, effulgentsia, EclipseGc, merlinofchaos: introduce Plugin System to core.