[Deskbar] Evolution Handler is now Sync, not Async

[Nigel Tao <nigel tao myrealbox com>]

Looking through the GNOME Launch Box code (ah, $DEITY bless open
source), I noticed that they do, amongst other things, evolution address
book completion.  And unlike contact-lookup-applet, they query
synchronously, not async'ly.

So evolution.py and the deskbar.evolution Python/C module are now sync,
which is simpler, without threads, locks, signals, or callbacks, and I
think less prone to crashing.  My personal address book is pretty small,
though, and I don't have an LDAP one, so I don't know if synchronous
querying is unviable from a performance / scalability perspective.

The async code is still there, but may not be bug-free.

Nigel.