Pipeline and action steps should support outputs

[kostas-vl]

In the new version of the pipeline syntax both pipelines and action should have support for outputs on each step. To provide an example for this functionality; similar to GitHub actions; the outputs would be an environment variable where each output is a key=value syntax separated by the new line character.

name: An example pipeline
type: pipeline
version: 3

jobs:
    main:
        - id: echo_command
          sh: echo "some_value=1000 >> $BLD_OUTPUT"

        - sh: echo ${{ steps.echo_command.outputs.some_value }}