Merge branch 'ce-port-3959-mirroring-interface-improvements' of https://gitlab.com/gitlab-org/gitlab-ce into ce-port-3959-mirroring-interface-improvements

Fix Vue datatype errors for markdownVersion parsing

See merge request gitlab-org/gitlab-ce!20800

Show decimal place up to single digit in Stacked Progress Bar

Closes gitlab-ee#6028

See merge request gitlab-org/gitlab-ce!20776

adds read_repository scope description

See merge request gitlab-org/gitlab-ce!20707

Bump nokogiri to 1.8.4 and sanitize to 4.6.6 for performance

See merge request gitlab-org/gitlab-ce!20795

Enable frozen string in app/serializers/**/*.rb

See merge request gitlab-org/gitlab-ce!20726

Add docs to disable proxy listener

See merge request gitlab-org/gitlab-ce!19734

Revert "Merge branch '2211-add-option-to-change-clone-path-docs' into 'master'"

See merge request gitlab-org/gitlab-ce!20633

In docs, add `No+Milestone` for querying by milestone

See merge request gitlab-org/gitlab-ce!20784

Annotate Gitlab::Git::Repository#fetch_ref

See merge request gitlab-org/gitlab-ce!20742

sanitize 4.6.6 has this optimization that will benefit Markdown rendering: https://github.com/rgrove/sanitize/pull/183

nokogiri 1.4.4 has this memory leak fix: https://github.com/sparklemotion/nokogiri/pull/1771

Add filter for minimal access level in groups and projects API

Closes #48165

See merge request gitlab-org/gitlab-ce!20478

Signed-off-by: Marko, Peter <peter.marko@siemens.com>

Signed-off-by: Marko, Peter <peter.marko@siemens.com>

Signed-off-by: Marko, Peter <peter.marko@siemens.com>

Improving performance of posting a comment by reducing memory + CPU

See merge request gitlab-org/gitlab-ce!20779