ci: force use of shared gitlab runner named "docker" and define the docker image as geaucassiopee/ci-cd-cross-platform-webapp:first

Refs #557

Refs #540

fix(ci): fall back on jalhyd devel branch instead of master if the requested jalhyd branch does not exists

This allows to run CI jobs on a nghyd developpement branch when the corresponding jalhyd branch has already been merged into devel.

refs #540

refs #526

refs #505

refs #505

deploy renamed to deploy-dev
deploy-stable renamed to deploy-prod

refs #505

Closes #495