Add an API and a <Make> function

[aplteam]

• The package now offers just its public interface, making the rest a black box.

  Note that the result of the (newly introduced) function Public defines what the public interface is.

• Namespace Admin with a function Make added.

  This required a change in the structure of the project.

  One can now ask Cider for how to build a new version:

        ]Cider.Make
  #.Sort.Admin.Make 1 ⍝ Execute this for creating a new version