API for getting overall status

[mpreisler]

This issue was originally created by @isimluk at the old repository called scap-client. Since it's valuable I have ported it to the new repository.

Hello Martin, here is an idead:

scap-client could provide API for getting some summary information about the scans results. It may return some details per tasks, but the main feature would be green/yellow/red type of information.

Green: If a periodic task is scheduled && the last result included passess && the last result did not include errors and fails.
Yellow: if no periodic task is scheduled
Red: Active task reports errors or fails.
Etc.

Maybe it might return different answers per tasks.

Thoughts?