Merge branch 'feature/project-export' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

Merge branches 'feature/project-export' and 'feature/project-import' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

Merge branches 'feature/project-export' and 'feature/project-import' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

Merge branches 'feature/project-export' and 'feature/project-import' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

Merge branch 'feature/project-export' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

Merge branches 'feature/project-export' and 'feature/project-import' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

added better error handling. Also refactored some of the code and fixed a few issues in project_tree_saver

Merge branch 'feature/project-export' of gitlab.com:gitlab-org/gitlab-ce into feature/project-import

# Conflicts:
#	app/models/project.rb

Remove `wall_enabled` field from Project



See merge request !4089

Improve multiple branch push performance by memoizing permission checking

See merge request !4091

Pass trusted_proxies to action_dispatch as IPAddrs instead of strings

Without this setting your own trusted_proxies does not work.

Fixes an issue introduce in: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3524

Fixes: https://gitlab.com/gitlab-org/gitlab-ce/issues/17004

See merge request !3970