Docs: Add automatic redirects to last batch of moved files

doc/api/build_triggers.md

doc/api/builds.md

doc/customization/welcome_message.md

doc/development/fe_guide/testing.md

doc/development/i18n_guide.md

doc/development/testing.md

doc/markdown/markdown.md

doc/operations/README.md

doc/operations/cleaning_up_redis_sessions.md

doc/operations/moving_repositories.md

doc/operations/sidekiq_memory_killer.md

doc/operations/unicorn.md

doc/pages/README.md

doc/pages/administration.md

doc/pages/getting_started_part_one.md

doc/pages/getting_started_part_three.md

doc/pages/getting_started_part_two.md

doc/raketasks/check.md

doc/raketasks/maintenance.md