Change external api for GenericBuilder class
- merge buildroot_prep and buildroot_resume under buildroot_conennect https://pagure.io/fm-orchestrator/issue/34 (idempotent movement)
- rename add_dependency to add_repo
- provide workflow comparison koji vs copr as a docstring
- update docstrings for GenericBuilder
Signed-off-by: Lubos Kocman <lkocman@redhat.com>