"kpm restore" offline should succeed if there is no dependency missing

- If we know an exact minimum version (version without *) and that version
  is availale in local packages folder -> done
- If '--ignore-failed-sources' is specified and we have a package that
  satisfies the version ranges -> done
- Otherwise exit with errors

parent #591 
FYI no need to initialize fields to default values (`false` is the default for `bool` anyway).