GitLab

In ".gitlab-ci.yml", added documentation and commented out "script" section in ".gitlab/ci/templates/deploy_stage_templates.yml".

In ".gitlab-ci.yml" and ".gitlab-ci-templates.yml", use "${...}" notation to expand variables instead of "$...".

Furthermore, added "manual" trigger to job template ".template_deploy_branch".

In ".gitlab-ci-templates.yml", added job template ".template_deploy_branch" which uses CI variables to create unique names and use this template in ".gitlab-ci.yml".

Refactored ".gitlab-ci.yml" completely and use templates combined with "include" and "extends" keyword.

This script was deleted in previous commit because it is not required anymory.