Foreman Maintain

Add --whitelist option

Allows to mark some steps to be ignored in the results: allows to
continue even when some checks are failing.

Full upgrade scenario

This commit intoroduces more structured upgrade scenario consisting of
this scenarios:

• pre_upgrade_check - non-modifying checks: is the system ready?
• pre_migrations - modifying procedures before source update
• migrations - source update and main migrations...

Assumeyes option

Improve reporting on hammer setup and preparation steps

Hammer setup preparation step

Support running commands interactively

RFE #23 - Add new status [WARNING] - Check: is system self registered

Decouple more reporter from runner

Before this commit, we required the reporter to call back runner
methods, which complicated the things. Also the multiple-steps select
was not working properly.

After this change, the reporter just returns a decision as result of...

Check count of paused tasks and offer next steps

Fixes #3 - Add option to skip the prompted step