Merge branch 'gitlab-ci' into 'master'

Add support for running builds directly from Gitlab CI

See merge request !20
8 jobs for master
Status Job ID Name Coverage
  Build
canceled #788
docker linux
build:debian:buster:i386

canceled #785
docker linux
build:debian:jessie:amd64

canceled #786
docker linux
build:debian:jessie:i386

canceled #789
docker linux
build:debian:sid:amd64

canceled #790
docker linux
build:debian:sid:i386

canceled #787
docker linux
build:debian:stretch:amd64

canceled #791
docker linux
build:ubuntu:trusty:amd64

canceled #792
docker linux
build:ubuntu:xenial:i386