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

Issue #2625696 by chx, benjy, alexpott, catch, mikeryan, andypost, phenaproxima: Make migrations themselves plugins instead of config entities

Revert "Issue #2625696 by chx, alexpott, benjy, mikeryan, andypost, phenaproxima: Make migrations themselves plugins instead of config entities"

This reverts commit 694994fe.

Issue #2625696 by chx, alexpott, benjy, mikeryan, andypost, phenaproxima: Make migrations themselves plugins instead of config entities

Issue #2557253 by phenaproxima, neclimdul: MigrateFullDrupalTestBase test discovery gobbles all the memory

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

Issue #697760 by sun: Replace getInfo() in tests with native phpDoc + annotations (following PHPUnit).

Issue #2121299 by andypost, bdone, benjy, penyaskito, chx, claudiu.cristea, damiankloip, gregboggs, InternetDevels, jessehs, jhedstrom, marvil07, mikeryan, pcambra, Xano, YesCT, axoplasm, kgoel, dclavain, jeckman, alvar0hurtad0, Drupali, fastangel, gloob, jhedstrom, joshtaylor, mpgeek, alexpott: Migrate Drupal 6 to Drupal 8