Add reference to step for each collected artifact

[i-keliukh]

Currently, Universum only reports artifacts themselves, but does not report the source steps that cause specific artifact to be collected. This is similar to #168.

[miltolstoy]

Resolved by https://github.com/Samsung/Universum/pull/718

from universum.configuration_support import Configuration, Step

step_artifacts = Configuration([dict(name="Step with artifacts",
                               command=["touch", "artifact1"],
                               artifacts="artifact1")])

configs = step_artifacts

5. Executing build steps
 |   5.1.  [ 1/1 ] Step with artifacts
 |      |   ==> Adding file .../universum_test/artifacts/Step_with_artifacts_log.txt to artifacts...
 |      |   ==> Execution log is redirected to file
 |      |   $ /usr/bin/touch artifact1
 |      └ [Success]
 |   
 |   5.2. Collecting artifacts for the 'Step with artifacts' step
 |      |   ==> Processing '.../universum_test/temp/artifact1'
 |      └ [Success]
 |   
 └ [Success]

6. Reporting build result
 |   ==> Here is the summarized build result:
 |   ==> 5. Executing build steps
 |   ==>   5.1.  [ 1/1 ] Step with artifacts - Success
 |   ==>   5.2. Collecting artifacts for the 'Step with artifacts' step - Success
 |   ==> Nowhere to report. Skipping...
 └ [Success]

@k-dovgan, please confirm and close the issue.