.gitlab-ci.yml: + pkg targets for some distros added + artifacts added - some distros were commented out (due to errors). misc/docker/*: + Dockerfiles updated with the necessary packages.
Add more Docker images with distributions (CentOS 8, Debian 10, Fedora 27-31, OpenSUSE 15.0 & 15.1, and Ubuntu 18.04 & 19.04). Fix some issues with older ones.
Add configuration and docker definitions for tests and builds in Gitlab CI platform. Some of them currently fail, which is a known problem.