initial commit of the CardDAV module

Originally from
https://github.com/LevelbossMike/Zarafa_Carddav/commit/db165788e2
CardDAV capable module for Zarafa 7

Code originally from https://github.com/LevelbossMike/Zarafa_Carddav has
been cleaned up and made compatible with Zarafa 7 mostly by Andreas
Brodowski and dw2412.
Merge pull request #3 from mcepl/carddav

CardDAV capable module for Zarafa 7