Provide status on the errors of the service's last announced manifest

[suvl]

A field should be added providing insight on the error level of the last announced manifest. That field should have three levels, as suggested (not final):

• OK: no errors
• WARN: the current errors won't let NAME know if there's anything wrong or not (dependencies do not have NAME installed or NAME version is invalid)
• ERR: all other errors not included in WARN