Merge dev.gitlab.org master into GitLab.com master

This merges all changes from dev.gitlab.org's master branch into the GitLab.com master branch.

Unfortunately, there are several conflicts that I do not feel comfortable resolving myself. These are the following conflicts:

• @nick.thomas: GITALY_SERVER_VERSION
• @smcgivern: app/controllers/projects/issues_controller.rb
• @engwan: app/policies/personal_snippet_policy.rb
• @fjsanpedro: app/views/layouts/nav/sidebar/_project.html.haml
• @stanhu: config/routes/import.rb
• @digitalmoksha: lib/banzai/pipeline/email_pipeline.rb
• @brodock: spec/features/markdown/math_spec.rb
• @brodock: spec/lib/safe_zip/extract_spec.rb
• @engwan: spec/policies/personal_snippet_policy_spec.rb
• @brodock: spec/services/members/destroy_service_spec.rb

If you are mentioned, please resolve these conflicts.