v0.1.17 Beta

Beta build for private distribution.

• New Delete page collects every repository-deletion control in one place:
  remove a single provisioned repo, bulk-remove an assignment's repos, delete
  unused starter kits, or remove an instructor copy. Deleting repositories
  requires the GitHub delete_repo scope.
• "Update" Actions opens pull requests to bring provisioned repos back in sync
  with an updated starter kit.
• Assignments can have an instructor-copy repository.
• Un-enrolled students no longer count toward dashboard and assignment totals.
• Fixes: Set Up button processing, Ctrl+0 reset zoom, New Term wizard.