Add support for gitlab-pages daemon

Will be released soon from https://gitlab.com/ayufan/gitlab-pages-poc

Add as a daemon.

Off by default.

Needs to have a set of listen address and ports configurations.

Needs to have access to the certs.

Independent of NGINX.

This is EE only.

cc @ayufan short notes I took during our call

mentioned in merge request !638 (merged)

Reassigned to @marin

Status changed to closed by merge request !638 (merged)

mentioned in commit 69239444

mentioned in commit a1335990

mentioned in commit 0bbaba4d