[horde] vcard 4.0 support

[lst_hoe02 at kwsoft.de]

Hello,

at the moment i'm playing around with distribution lists and have  
noticed that there is no support to sync distributions list for  
example with CardDAV because vcard 3.0 (RFC 2426) used by Horde has no  
way to transfer groups in a portable way. The vcard 4.0 (RFC 6350)  
would have support for groups so it might be useful to switch to vcard  
4.0, no? Can anyone with more knowledge share some inside what  
steps/modules would be involved to get Horde working with vcard 4.0 ?

Thanks

Andreas