Add 'name'/'title'/'label' field to jobs as display name in UI

As developers, we often like use basic, boring but robust variable and function names. The same would hold for jobs in the .gitlab-ci.yml file.

For example, while

Build Job:
  script: echo "Hello World"

is perfectly valid, it feels unnatural. We much rather prefer to

build_job:
  script: echo "Hello World"

However this looks ugly in the UI.

I thus propose to add a 'name' tag, which is only for display purposes (and can hold any string and can expand certain variables) and matches with workflow:name

build_job:
  name: "Build Job"
  script: echo "Hello World"

If unset, the current behavior holds (e.g. copy job names minus : into the name field. Ideally this would also be done for stages, but I think that is less then trivial