Rework :box-add argument handling.
Rework :box-add argument handling.

The new handling mechanism will apply quoted maps of constraints to
subsequent project names.

For example:

 lein voom :box-add '{:branch "master"}' my-organization/my-project

This lets us express :branch, :repo, :path and :version constraints on
a specified project.

LonoCloud/lein-voom