Adding additional pipeline cases

• bash-workarounds
  Pipeline with some examples escaping bash or yaml limitations
• cache-between-jobs
  Pipeline sharing dependencies, code and reports generated on one job to the next one
• conditional-jobs
  Pipeline with 4 jobs with different conditionals:
  -- runs on master branch
  -- on non-master branches, and if commit message does not contain [new-feature-release] between brackets"
  -- manual push
  -- disabled job
• docker-custom-image
  creating custom docker image example, pushed to GitLab project registry:
  -- 1) generating a custom docker image
  -- 2) running jobs on that custom image
• git-reference-cache
  git reference cache ("git clone --reference") usage example, optimization passing from 50 to 8 min running time:
  -- 1) generating one custom docker image, with a full git clone on a local folder
  -- 2) using that custom image, running a "git clone --reference" pointing to that folder
• git-swallow-clone
  pipeline specifying a swallow clone ("git clone --depth 1") at project and job level, optimization passing from 43 to 1 min running time
• notification-on-failure
  pipeline with a jobs sending notifications to a slack notification (by curl) on pipeline start, on failure and on success
• pipeline-include-template
  yaml template example:
  -- 1) working like a "shared library", containing some common used commands
  -- 2) importing that shared pipeline, and refering that common parts
• pipeline-multi-project
  example of how to trigger one pipeline as a job from another pipeline (multi project pipeline)
• vars-array
  pipeline reading variable values from predefined values like an array
• vars-between-jobs
  pipeline passing variable values from one job to another one, using dotnet artifacts