Implement Coverity checker and include triaged defects

[JasperCraeghs]

We want to complete #74 and add support for this checker to the code-quality-report feature.

The classification of the defect shall determine the severity string. Every classification included in this configuration, will be included in the code quality report, and, by default, they will be counted towards the warnings limit. You can exclude a classification from the count. Any classification not included in this configuration, will be ignored. Example configuration:

{
    "intentional": {"severity": "info", "count": False},
    "bug": {"severity": "major"},
    "pending": {"severity": "critical"},
}

What do you think, @Letme ?

[Letme]

Sounds what we want yes and also severity is OK.