Allow artifact naming for reference

[treyhyde]

Artifacts are named via their repository name which is potentially long, dotted, backslashed, underscored, and non-unique.
It would be desirable to name: these artifacts for reference purposes. In theory this would also allow me to build multiple images in the same repository and differ them in the app based on tag strategy.

Our use case is we run continuous experiments for the same project with say... differing settings or build parameters. It is the same code base and branch and thus multiple artifacts in one docker repo. We're forced to create a new repo for every experiment with skaffold where it would be easier to have a tag template such as EXPERIMENT_NAME+GIT_HASH or something similar.