CardDAV server

Finally! was able put together the functional part of vCard server tonight.

Kudos to Evert at SabreDAV

In case anyone else is working on a server side script to manage the CardDAV, instead of an http request from the client, you can opt to:

1. setup PDO
2. create Sabre_CardDAV_Backend_PDO
3. store a vCard into a String
4. create a new card, Sabre_CardDAV_Backend_PDO->CreateCard()