Add prefix (Guanako/Valama) to console messages.

 * Fix some message types (error, warning).
Fix debug output (remove comma at EOL)
Support custom vapi for package.

 * Support empty extracheck with just a custom vapi.
Guanako: Support custom vapis as packages.
Valama: Don't add same vapi twice.
Guanako: Search for pkg by name.