Remove assumption in test about presence of a git config

The tests listed below run git commit which fails when a git config does not provide user.e-mail.

+ test/test-ghe-backup-repositories-rsync.sh
+ test/test-ghe-restore.sh
+ test/test-ghe-backup.sh
Rename libexec to lib

Debian does not provide a libexec, needed for #49.
Add debian packaging