#4 syncitems mode support

[Benjamin Ragheb]

I'm currently working on this. At the moment I am creating two
new objects: LJSyncItem and LJSyncItemsSession. The idea is that
you will set a delegate of LJSyncItemsSession and call -sync to
receive information via callbacks.

The session object could be archived (perhaps as account
customInfo), thus retaining the last sync date internally.