Add --version flag to archive subcommand.

This adds a --version flag to the archive subcommand. When set, the project version will be included in the Immutant archive name. Needs a supporting change to deploy-tools, sent in a separate pull request.

Rationale: for deployment, we push the .ima files up to artifactory using the lein-package plugin. This requires the project version in the .ima filename. Happy to consider other approaches if this pull request is not the way to go.