Docs: add admin index

Closes #4222

See merge request gitlab-org/gitlab-ee!3664

Attach files (including images) to epic description

Closes #3938

See merge request gitlab-org/gitlab-ee!3510

ProtectedBranches API handles per user/group granularity

Closes #4131

See merge request gitlab-org/gitlab-ee!3516

Update push_rules.md

See merge request gitlab-org/gitlab-ee!3660

Support mentioning epics

Closes #3853

See merge request gitlab-org/gitlab-ee!3615

Allows admins to disable mirroring

Closes #3730

See merge request gitlab-org/gitlab-ee!3586

Port of Resolve "Display member role per project" to EE

See merge request gitlab-org/gitlab-ee!3525

# Conflicts:
#   db/schema.rb

Port from CE: The API isn't using the appropriate services for managing forks

Closes gitlab-ce#40752

See merge request gitlab-org/gitlab-ee!3659

Updated geo-overview.png

Closes #4106

See merge request gitlab-org/gitlab-ee!3650

List multiple clusters EE

Closes #3734

See merge request gitlab-org/gitlab-ee!3644

Simplifying the configuration page

See merge request gitlab-org/gitlab-ee!3599

Merge branch '4242-failure-in-spec-ee-spec-services-ee-projects-hashed_storage-migrate_attachments_service_spec-rb' into 'master'

Resolve "Failure in spec/ee/spec/services/ee/projects/hashed_storage/migrate_attachments_service_spec.rb"

See merge request gitlab-org/gitlab-ee!3653

[EE] Move the "Limit conflicts with EE" doc to "Automatic CE-> EE merge"

See merge request gitlab-org/gitlab-ee!3658

Add example with number and parentheses

See merge request gitlab-org/gitlab-ee!3649

Signed-off-by: Rémy Coutable <remy@rymai.me>

Renames remote_mirror_available to mirror_available to not only incorporate push mirrors but pull mirrors as well.

Fix board filter when milestone is  predefined

Closes gitlab-ce#40654

See merge request gitlab-org/gitlab-ee!3605

Running this after
spec/services/projects/hashed_storage_migration_service_spec.rb would fail
previously, because the repository already existed on disk. As this spec expects
the repository to not exist on disk prior to being created, we should clear out
the test repos before running.

Downgrade the grpc gem to 1.4.5

See merge request gitlab-org/gitlab-ee!3642

Move git operations for squash and rebase into Gitlab::Git

Closes gitaly#761

See merge request gitlab-org/gitlab-ee!3543