* lib/lehti/cli.scm: use r7rs
* lib/lehti/command/bundle.scm: use r7rs
* lib/lehti/command/clean.scm: use r7rs, add message
* lib/lehti/command/commands.scm: use r7rs
* lib/lehti/command/environment.scm: use r7rs
* lib/lehti/command/list.scm: use r7rs
* lib/lehti/command/projects.scm,search.scm: use r7rs
* lib/lehti/command/setup.scm: use r7rs
* lib/lehti/command/specification.scm: use r7rs