API-Server provided custom image

[Thomas2500]

Add the possibility to show a custom image and description instead of the country flag for specific websites. This is specially used for domains which resolve to an internal IP.

• [x] Custom server provided icon (eventually base64 encoded image)
• [ ] Custom description instead / in addition to country information

This can be useful for company internal use (selfhosted instance) to show information like responsible person, contact person, internal location of service (DC01, VIE/FRA, EXT-IN), path (Internal/External) ...

This will only be available on selfhosted instances of the uDomainFlag server software. The public server will not return any company logos/data to users.