allow to do propfinds on hugh addressbooks independent of memory_limit:
- regular groupdav_handler::profind() method gets split in a method just
computing a filter and a callback to run that filter on the backend
- groupdav_propfind_iterator class is returned from profind method
instead of an array with information about the files
- iterator calls groupdav_hander::propfind_callback if there are no more
entries from the previous call
- constructor of groupdav_propfind_iterator allows to pass an extra array
with files to return, to simplify modifying existing implementation
(were eg. information about the current path, get's supplied from
calling groupdav class).
manufacturer and the recogniced GroupDAV client as product name.
This way we are able to handle different GroupDAV clients, as we
allready do with different SyncML clients.
Also removed the no longer needed code enabling the use of the real UID,
as SyncML does no longer misuse the UID for it's GUID.
addressbook (infolog will follow).
CalDAV is tested so far with lightning 0.8 and Apple's iCal. Please note
that both distinguish between iCalServer and CalDAV!
The URL is currently http://domain.com/egroupware/groupdav.php/calendar/
