Issue #2917883 by quietone, TR, Jo Fitzgerald, masipila, phenaproxima: Rename 'migration_templates' directories in core modules to 'migrations'

Issue #2857681 by Jo Fitzgerald, quietone: Comments not starting with a capital letter in d6_file.yml & d7_file.yml

Issue #2826047 by heddn, Jo Fitzgerald, mikeryan, catch, alexpott: 6-8 user picture migration must create new fids, which can conflict with fids used by other migrations

Issue #2857502 by Jo Fitzgerald, shashikant_chauhan, quietone, heddn: Comment out migration of D6 file size to sync with D7

Issue #2818155 by Yogesh Pawar, edgewl2: Add comments to d6_file stating the conflicts with d6_user_picture_file

Issue #2695297 by mikeryan, ohthehugemanatee, quietone, vasi, Sharique, chx, benjy, phenaproxima, heddn, benjifisher: Refactor EntityFile and use process plugins instead

Revert "Issue #2560795 by mikeryan, phenaproxima, penyaskito, willwh, benjy: Source plugins have a hidden dependency on migrate_drupal"

This reverts commit 89815ba3.

Issue #2560795 by mikeryan, phenaproxima, penyaskito, willwh, benjy: Source plugins have a hidden dependency on migrate_drupal

Issue #2534012 by phenaproxima, hussainweb, mikeryan: Move module-specific migration support into the file module

Issue #2463909 by phenaproxima, mikeryan: Migrations should support non-installed default configurations (templates)

Issue #2460529 by alexpott, chx, phenaproxima: Migrations need to use the configuration entity dependency system

Issue #2466797 by mikeryan, benjy: Rename migration_groups key to avoid confusion with MigrationGroup support

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